Document:

<PAGE>

                                                                     Exhibit 4.8

NEITHER THIS WARRANT NOR ANY SECURITIES PURCHASABLE UPON EXERCISE HEREOF HAVE
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE SECURITIES LAWS.
THIS WARRANT HAS BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO
DISTRIBUTION OR RESALE, AND NEITHER THIS WARRANT NOR ANY SECURITIES PURCHASABLE
UPON EXERCISE HEREOF MAY BE SOLD OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE
REGISTRATION STATEMENT FOR SUCH SHARES UNDER THE SECURITIES ACT OF 1933 AND ANY
APPLICABLE STATE SECURITIES LAWS, OR EVIDENCE REASONABLY SATISFACTORY TO THE
COMPANY THAT REGISTRATION IS NOT REQUIRED UNDER SUCH ACT AND LAWS.

Warrant No. W-B-[_______]                                       [_______] Shares
May 1, 2001

                              COMMON STOCK WARRANT

                             To Purchase Shares of

                                  Common Stock

                                       of

                          SPECTRA SCIENCE CORPORATION

     THIS CERTIFIES THAT, for value received,[__________] ("Holder"), or its
assigns, is entitled, subject to the terms set forth below, to purchase from
Spectra Science Corporation (the "Company"), [_________] fully paid and
non-assessable shares of the Common Stock, $.O1 par value per share ("Common
Stock"), of the Company at a purchase price of $7.50 per share (subject to
adjustment as set forth herein, the "Warrant Price"). The number and character
of, and purchase price for, such shares of Common Stock are subject to
adjustment as provided herein. This Warrant is immediately exercisable and will
remain exercisable until and unless this Warrant has expired as provided herein.

     This Warrant has been issued in connection with the Company's investment in
SpectraDisc Corporation pursuant to a Common Stock and Preferred Stock Purchase
Agreement

<PAGE>

dated as of June 30, 1999, among SpectraDisc Corporation, the Company, and the
persons named as Purchasers therein.

     1.   Exercise of Warrant.

          1.1 Exercise. This Warrant may be exercised by the holder hereof in
whole or in part (but not as to fractional shares of Common Stock) by the
surrender of this Warrant and delivery of an executed Notice of Exercise in the
form appended hereto duly executed by such holder to the Company at its
principal office at any time or times within the period specified above,
accompanied by payment for the Common Stock as to which this Warrant is being
exercised by wire transfer to an account designated by the Company or by
certified or bank check. In the event of a partial exercise of this Warrant,
this Warrant will be canceled and the Company will deliver a new Warrant of like
tenor representing the balance of the share of Common Stock purchasable
hereunder. Alternatively, the holder hereof may elect to exercise the rights
represented by this Warrant in whole or in part (but not as to fractional shares
of Common Stock) by the surrender of this Warrant and delivery of an executed
Notice of Exercise specifying that the value (as determined below) of this
Warrant shall be the consideration for the shares of Common Stock, in which
event the Company shall issue to the holder a number of shares of Common Stock
computed using the following formula:

       X = Y (A-B)
           -------
              A

Where: X = the number of shares of Common Stock to be issued to the holder.
       Y = the number of shares of Common Stock issuable upon exercise of this
           Warrant on the date of delivery of the Notice of Exercise.
       A = the current fair market value of one share of Common Stock.
       B = Warrant Price.

     As used herein, current fair market value of the Common Stock shall mean
the numerical average of fair market value per share of Common Stock over a
period of 21 days consisting of the day on which the Notice of Exercise is
received by the Company and the 20 consecutive business days prior to such day.
The fair market value per share of Common Stock for any day shall mean the
average of the closing prices of the Company's Common Stock sold on all
securities exchanges on which the Common Stock may at the time be listed or as
quoted on the Nasdaq system, or, if there have been no sales on any such
exchange or any such quotation on any day, the average of the highest bid and
lowest asked prices on all such exchanges or such Nasdaq system at the end of
such day, or, if on any day the Common Stock is not so listed, the average of
the representative bid and asked prices quoted in the Nasdaq system as of 4:00
p.m., New York City time, or, if on any day the Common Stock is not quoted in
the Nasdaq system, the average of the highest bid and lowest asked price on such
day in the domestic over-the-counter market as reported by the National
Quotation Bureau, Incorporated, or any similar successor organization. If at any
time the Common Stock is not listed on any securities exchange or quoted in the
Nasdaq system or the over-the-counter market, the current fair market value of

                                      -2-

<PAGE>

Common Stock shall be the highest price per share which the Company could obtain
from a willing buyer (not a current employee or director) for shares of Common
Stock sold by the Company, from authorized but unissued shares, as determined in
good faith by the Board of Directors of the Company. Notwithstanding the
foregoing, if the Company shall engage in an Acquisition Transaction, as defined
below, the current fair market value of the Common Stock shall be determined
with reference to the value ascribed to the Company by the terms of the
Acquisition Transaction. An "Acquisition Transaction" is (i) the closing of the
sale of all or substantially all of the assets of the Company or (ii) a
consolidation or merger or other business combination to which more than 50% of
the equity ownership of the Company (calculated on a fully-diluted basis) has
been transferred.

          1.2 Delivery of Stock Certificates, etc., on Exercise. As soon as
practicable after the exercise of this Warrant in full and in any event within
10 days thereafter, the Company at its expense will cause to be issued in the
name of and delivered to the holder hereof, or as such holder (upon payment by
such holder of any applicable transfer taxes) may direct, a certificate or
certificates for the number of fully paid and nonassessable shares of Common
Stock to which such holder shall be entitled on such exercise.

          1.3 Expiration. This Warrant will expire and be of no further force or
effect at 5 p.m. on June 30, 2009.

     2.   Adjustments for Certain Events.

          2.1 Stock Splits, etc. In case the Company shall at any time subdivide
its outstanding shares of Common Stock into a greater number of shares, the
Warrant Price in effect immediately prior to such subdivision shall be
proportionately reduced, and the number of shares of Common Stock issuable upon
exercise of this Warrant shall be proportionately increased; and conversely, in
case the outstanding shares of Common Stock of the Company shall be combined
into a smaller number of shares, the Warrant Price in effect immediately prior
to such combination shall be proportionately increased and the number of shares
of Common Stock issuable upon exercise of this Warrant shall be proportionately
reduced.

          2.2 Adjustments for Capital Reorganization or Reclassification. If any
capital reorganization or reclassification of the capital stock of the Company
shall be effected, then, as a condition of such capital reorganization or
reclassification, lawful and adequate provision shall be made whereby the holder
hereof shall thereafter have the right to purchase and receive upon the basis
and upon the terms and conditions specified in this Warrant, in lieu of shares
of Common Stock of the Company immediately theretofore purchasable and
receivable upon the exercise of the rights represented hereby, those shares of
stock, securities or assets which would have been issued or payable with respect
to or in exchange for the Common Stock issuable upon exercise of this Warrant
had this Warrant been exercised immediately prior to the record date (or the
effective date, as the case may be) for such capital reorganization or
reclassification.

                                      -3-

<PAGE>

          2.3 Acquisition Transaction. The Company shall provide to the holder
of this Warrant written notice not less than thirty (30) business days prior to
the anticipated closing of an Acquisition Transaction of the anticipated closing
of such transaction and a brief summary of the business terms thereof. The
holder of this Warrant will in such case be entitled to exercise this Warrant,
effective immediately prior to the closing of the Acquisition Transaction
(subject to the completion of such closing), as provided in Section 1.1 hereof
by delivery of an executed Notice of Exercise and payment of the exercise price
not less than five (5) days prior to such closing. In the event the closing of
an Acquisition Transaction does not occur for any reason, such Notice of
Exercise will be of no force or effect.

          2.4 Notice of Adjustments. Upon any adjustment of the Warrant Price,
the Company shall give written notice thereof, by first class mail, postage
prepaid, addressed to the holder of this Warrant at its address registered on
the books of the Company, which notice shall state the Warrant Price resulting
from such adjustment and the increased or decreased number of shares purchasable
at such price upon the exercise of this Warrant, setting forth in reasonable
detail the method of calculation and the facts upon which such calculation is
based.

     3. Liquidating Dividends. If the Company pays a dividend or makes a
distribution on the Common Stock payable otherwise than in cash out of earnings
or earned surplus (determined in accordance with generally accepted accounting
principles) except for a stock dividend payable in shares of Common Stock (a
"Liquidating Dividend"), then the Company will pay or distribute to the holder
of this Warrant, upon the exercise hereof, in addition to the Common Stock
purchased upon such exercise, the Liquidating Dividend which would have been
paid to such holder if it had been the owner of record of such shares of Common
Stock immediately prior to the date on which a record is taken for such
Liquidating Dividend or, if no record is taken, the date as of which the record
holders of Common Stock entitled to such dividends or distribution are to be
determined.

     4. Notice of Liquidation, etc. In the event of any voluntary or involuntary
dissolution, liquidation or winding-up of the Company, the Company not less than
ten (10) days prior to the occurrence of such event will give to the holder of
this Warrant written notice of (i) the date on which any such dissolution,
liquidation or winding-up is to take place, (ii) the amount and character of
assets, including any stock or other securities, proposed to be issued or
granted and (iii) the persons or class of persons to whom such proposed issue or
grant is to be made.

     5. Lock-up. The holder of this Warrant agrees not to sell or otherwise
transfer any shares of Common Stock issued or issuable upon exercise of this
Warrant for a period of up to 180 days following the closing of the Company's
initial public offering, provided the underwriters of the offering have
requested that directors, executive officers and other stockholders of the
Company agree not to sell or transfer shares of Common Stock during such period.

                                      -4-

<PAGE>

     6. Reservation of Stock, etc., Issuable on Exercise of Warrants. The
Company will at all times reserve and keep available, solely for issuance and
delivery on the exercise of the Warrant, all shares of Common Stock from time to
time issuable on the exercise of the Warrant.

     7. Voting Rights. This Warrant shall not entitle the holder hereof to
voting rights or any other rights whatsoever as a stockholder of the Company or,
except as set forth in Section 4 above, to any notice of meetings of
stockholders or any other proceedings of the Company.

     8. Exchange of Warrant. Subject to compliance with applicable securities
laws, this Warrant is exchangeable, upon the surrender hereof at the principal
office of the Company, for new Warrants of like tenor representing in the
aggregate the right to subscribe for and purchase the number of shares of Common
Stock which may be subscribed for and purchased hereunder, each of such new
Warrants to represent the right to subscribe for and purchase such number of
shares of Common Stock as shall be designated by such holder hereof at the time
of such surrender.

     9. Transferability. Subject to compliance with applicable securities laws,
this Warrant and all rights hereunder are transferable at the principal office
of the Company by the holder hereof in person or by duly authorized attorney,
upon surrender of this Warrant properly endorsed, together with a written
assignment of this Warrant duly executed by the holder hereof or its duly
authorized attorney. Each taker and holder of this Warrant, by taking or holding
the same, consents and agrees that this Warrant, when endorsed in blank, shall
be deemed negotiable, and that the holder hereof, when this Warrant shall have
been so endorsed, may be treated by the Company and all other persons dealing
with this Warrant as the absolute owner hereof for any purpose and as the person
entitled to exercise the rights represented by this Warrant, or to the transfer
hereof on the books of the Company, any notice to the contrary notwithstanding;
but until such transfer on such books, the Company may treat the holder hereof
as the owner for all purposes.

     10. Miscellaneous. The provisions of this Warrant may be amended or waived
only by an instrument in writing signed by the party against which enforcement
of such amendment or waiver is sought. This Warrant shall be construed and
enforced in accordance with and governed by the laws of the State of Delaware.
The headings in this Warrant are for purposes of reference only, and shall not
limit or otherwise affect any of the terms hereof. This Warrant is being
executed as an instrument under seal. The invalidity or unenforceability of any
provision hereof shall in no way affect the validity or enforceability of any
other provision.

                                      -5-

<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by an
officer thereunto duly authorized as of May 1, 2001.

                                             By:
                                                --------------------------------
                                                Name:  Nabil Lawandy
                                                Title: President

Attest:

-----------------------------------

                                      -6-

<PAGE>

                               NOTICE OF EXERCISE

                               (To be Executed by
                              the Registered Holder
                        in Order to Exercise the Warrant)

     The undersigned hereby irrevocably elects to exercise the right to purchase
                        (__________) shares of Common Stock, $.01 par value, of
-----------------------
Spectra Science Corporation; covered by Warrant No. W-[_] according to the
conditions thereof and herewith makes payment of the Warrant Price of such
shares in full.

     Specify method of exercise by check mark:

1.   Such payment is hereby made in the amount of $_____________ by wire
     transfer or by certified or bank check.

2.   The holder elects to receive shares for the value (as determined pursuant
     to Section 1.1 of the Warrant) of the Warrant.

                                  Printed Name
                                  of Warrant Holder:
                                                     ---------------------------

                                  Signature:
                                             -----------------------------------

                                  Title (if signing
                                  on behalf of a
                                  Warrant Holder:
                                                  ------------------------------

                                  Address:
                                           -------------------------------------

                                           -------------------------------------

                                           -------------------------------------

Dated:
      ------------------------

                                      -7-<PAGE>

                                                                     Exhibit 4.9

NEITHER THIS WARRANT NOR ANY SECURITIES PURCHASABLE UPON EXERCISE HEREOF HAVE
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE SECURITIES LAWS.
THIS WARRANT HAS BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO
DISTRIBUTION OR RESALE, AND NEITHER THIS WARRANT NOR ANY SECURITIES PURCHASABLE
UPON EXERCISE HEREOF MAY BE SOLD OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE
REGISTRATION STATEMENT FOR SUCH SHARES UNDER THE SECURITIES ACT OF 1933 AND ANY
APPLICABLE STATE SECURITIES LAWS, OR EVIDENCE REASONABLY SATISFACTORY TO THE
COMPANY THAT REGISTRATION IS NOT REQUIRED UNDER SUCH ACT AND LAWS.

Warrant No. WD(ii)-[_______]                                  [_______]Shares

                                    WARRANT

                             To Purchase Shares of

                                  Common Stock

                                       of

                          SPECTRA SCIENCE CORPORATION

     This certifies that, for value received, [_______]("Holder"), or its
assigns, is entitled, subject to the terms set forth below, to purchase from
Spectra Science Corporation (the "Company"), [_______] fully paid and
non-assessable shares of the Common Stock, $.01 par value per share ("Common
Stock"), of the Company at a purchase price of $2.50 per share (subject to
adjustment as set forth herein, the "Warrant Price"). The number and character
of, and purchase price for, such shares of Common Stock are subject to
adjustment as provided herein. This Warrant is immediately exercisable and will
remain exercisable until and unless this Warrant has expired as provided herein.

1.   Exercise of Warrant.

     1.1 Exercise. This Warrant may be exercised by the holder hereof in whole
or in part (but not as to fractional shares of Common Stock) by the surrender of
this Warrant and delivery of an executed Notice of Exercise in the form appended
hereto duly executed by such holder to the Company at its principal office at
any time or times within the period specified above, accompanied by payment for
the Common Stock as to which this Warrant is being exercised by wire transfer to
an account designated by the Company or by certified or bank check. In the event
of a partial exercise of this Warrant, this Warrant will be canceled and the
Company will deliver a new Warrant of like tenor representing the balance of the
shares of Common Stock purchasable hereunder. Alternatively, the holder hereof
may elect to exercise the rights represented by this Warrant in whole or in part
(but not as to fractional shares of Common Stock) by the surrender of this
Warrant and delivery of an executed Notice of Exercise specifying that the value
(as determined below) of this Warrant shall be the consideration for the

<PAGE>

shares of Common Stock, in which event the Company shall issue to the holder a
number of shares of Common Stock computed using the following formula:

<PAGE>

                                   X = Y(A-B)
                                       ------
                                          A

Where:

     X = the number of shares of Common Stock to be issued to the holder;

     Y = the number of shares of Common Stock issuable upon exercise of this
         Warrant on the date of delivery of the Notice of Exercise;

     A = the current fair market value of one share of Common Stock; and

     B = the Warrant Price.

     As used herein, current fair market value of the Common Stock shall mean
the numerical average of the fair market value per share of Common Stock over a
period of 21 days consisting of the day on which the Notice of Exercise is
received by the Company and the 20 consecutive business days prior to such day.
The fair market value per share of Common Stock for any day shall mean the
average of the closing prices of the Company's Common Stock sold on all
securities exchanges on which the Common Stock may at the time be listed or as
quoted on the Nasdaq system, or, if there have been no sales on any such
exchange or any such quotation on any day, the average of the highest bid and
lowest asked prices on all such exchanges or such Nasdaq system at the end of
such day, or, if on any day the Common Stock is not so listed, the average of
the representative bid and asked prices quoted in the Nasdaq system as of 4:00
p.m., New York City time, or, if on any day the Common Stock is not quoted in
the Nasdaq system, the average of the highest bid and lowest asked price on such
day in the domestic over-the-counter market as reported by the National
Quotation Bureau, Incorporated, or any similar successor organization. If at any
time the Common Stock is not listed on any securities exchange or quoted in the
Nasdaq system or the over-the-counter market, the current fair market value of
Common Stock shall be the highest price per share which the Company could obtain
from a willing buyer (not a current employee or director) for shares of Common
Stock sold by the Company, from authorized but unissued shares, as determined in
good faith by the Board of Directors of the Company. Notwithstanding the
foregoing, if the Company shall engage in an Acquisition Transaction, as defined
below, the current fair market value of the Common Stock shall be determined
with reference to the value ascribed to the Company by the terms of the
Acquisition Transaction. An "Acquisition Transaction" is (i) the closing of the
sale of all or substantially all of the assets of the Company or (ii) a
consolidation or merger or other business combination to which more than 50% of
the equity ownership of the Company (calculated on a fully-diluted basis) has
been transferred.

     1.2 Delivery of Stock Certificates, etc., on Exercise. As soon as
practicable after the exercise of this Warrant in full and in any event within
10 days thereafter, the Company, at its expense, will cause to be issued in the
name of and delivered to the holder hereof, or as such holder (upon payment by
such holder of any applicable transfer taxes) may direct, a certificate or
certificates for the number of fully paid and non-assessable shares of Common
Stock to which such holder shall be entitled on such exercise.

     1.3 Expiration. This Warrant will expire and be of no further force or
effect at 5 p.m. on the date five years from the date hereof.

<PAGE>

2.   Adjustments for Certain Events.

     2.1 Stock Splits, etc. In case the Company shall at any time subdivide its
outstanding shares of Common Stock into a greater number of shares, the Warrant
Price in effect immediately prior to such subdivision shall be proportionately
reduced, and the number of shares of Common Stock issuable upon exercise of this
Warrant shall be proportionately increased; and conversely, in case the
outstanding shares of Common Stock of the Company shall be combined into a
smaller number of shares, the Warrant Price in effect immediately prior to such
combination shall be proportionately increased and the number of shares of
Common Stock issuable upon exercise of this Warrant shall be proportionately
reduced.

     2.2 Adjustments for Capital Reorganization or Reclassification. If any
capital reorganization or reclassification of the capital stock of the Company
shall be effected, then, as a condition of such capital reorganization or
reclassification, lawful and adequate provision shall be made whereby the holder
hereof shall thereafter have the right to purchase and receive upon the basis
and upon the terms and conditions specified in this Warrant, in lieu of shares
of Common Stock of the Company immediately theretofore purchasable and
receivable upon the exercise of the rights represented hereby, those shares of
stock, securities or assets which would have been issued or payable with respect
to or in exchange for the Common Stock issuable upon exercise of this Warrant
had this Warrant been exercised immediately prior to the record date (or the
effective date, as the case may be) for such capital reorganization or
reclassification.

     2.3 Acquisition Transaction. The Company shall provide to the holder of
this Warrant written notice not less than thirty business days prior to the
anticipated closing of an Acquisition Transaction of the anticipated closing of
such transaction and a brief summary of the business terms thereof. The holder
of this Warrant will in such case be entitled to exercise this Warrant,
effective immediately prior to the closing of the Acquisition Transaction
(subject to the completion of such closing), as provided in Section 1.1 hereof
by delivery of an executed Notice of Exercise and payment of the exercise price
not less than five days prior to such closing. In the event the closing of an
Acquisition Transaction does not occur for any reason, such Notice of Exercise
will be of no force or effect.

     2.4 Notice of Adjustments. Upon any adjustment of the Warrant Price, the
Company shall give written notice thereof, by first class mail, postage prepaid,
addressed to the holder of this Warrant at his, her, or its address registered
on the books of the Company, which notice shall state the Warrant Price
resulting from such adjustment and the increased or decreased number of shares
purchasable at such price upon the exercise of this Warrant, setting forth in
reasonable detail the method of calculation and the facts upon which such
calculation is based.

3. Liquidating Dividends. If the Company pays a dividend or makes a distribution
on the Common Stock payable otherwise than in cash out of earnings or earned
surplus (determined in accordance with generally accepted accounting principles,
consistently applied) except for a stock dividend payable in shares of Common
Stock (a "Liquidating Dividend"), then the Company will pay or distribute to the
holder of this Warrant, upon the exercise hereof, in addition to the Common
Stock purchased upon such exercise, the Liquidating Dividend which would have
been paid to such holder if it had been the owner of record of such shares of
Common Stock immediately prior to the date on which a record is taken for such
Liquidating Dividend or, if no record is taken, the date as of which the record
holders of Common Stock entitled to such dividends or distribution are to be
determined.

<PAGE>

4. Notice of Liquidation, etc. In the event of any voluntary or involuntary
dissolution, liquidation or winding-up of the Company, the Company not less than
ten days prior to the occurrence of such event will give to the holder of this
Warrant written notice of(i) the date on which any such dissolution, liquidation
or winding-up is to take place, (ii) the amount and character of assets,
including any stock or other securities, proposed to be issued or granted, and
(iii) the persons or class of persons to whom such proposed issue or grant is to
be made.

5. Lock-up. The holder of this Warrant agrees not to sell or otherwise transfer
any shares of Common Stock issued or issuable upon exercise of this Warrant for
a period of up to 180 days following the closing of the Company's initial public
offering, provided the underwriters of the offering have requested that
directors, executive officers and other stockholders of the Company agree not to
sell or transfer shares of Common Stock during such period.

6. Reservation of Stock, etc., Issuable on Exercise of Warrants. The Company
will at all times reserve and keep available, solely for issuance and delivery
on the exercise of the Warrant, all shares of Common Stock from time to time
issuable on the exercise of the Warrant.

7. Voting Rights. This Warrant shall not entitle the holder hereof to voting
rights or any other rights whatsoever as a stockholder of the Company or, except
as set forth in Section 4 above, to any notice of meetings of stockholders or
any other proceedings of the Company.

8. Exchange of Warrant. Subject to compliance with applicable securities laws,
this Warrant is exchangeable, upon the surrender hereof at the principal office
of the Company, for new Warrants of like tenor representing in the aggregate the
right to subscribe for and purchase the number of shares of Common Stock which
may be subscribed for and purchased hereunder, each of such new Warrants to
represent the right to subscribe for and purchase such number of shares of
Common Stock as shall be designated by such holder hereof at the time of such
surrender.

9. Transferability. Subject to compliance with applicable securities laws, this
Warrant and all rights hereunder are transferable at the principal office of the
Company by the holder hereof in person or by duly authorized attorney, upon
surrender of this Warrant properly endorsed, together with a written assignment
of this Warrant duly executed by the holder hereof or its duly authorized
attorney. Each taker and holder of this Warrant, by taking or holding the same,
consents and agrees that this Warrant, when endorsed in blank, shall be deemed
negotiable, and that the holder hereof, when this Warrant shall have been so
endorsed, may be treated by the Company and all other persons dealing with this
Warrant as the absolute owner hereof for any purpose and as the person entitled
to exercise the rights represented by this Warrant, or to the transfer hereof on
the books of the Company, any notice to the contrary notwithstanding; but until
such transfer on such books, the Company may treat the holder hereof as the
owner for all purposes.

<PAGE>

10. Miscellaneous. The provisions of this Warrant may be amended or waived only
by an instrument in writing signed by the party against which enforcement of
such amendment or waiver is sought. This Warrant shall be construed and enforced
in accordance with and governed by the laws of the State of Delaware. The
headings in this Warrant are for purposes of reference only, and shall not limit
or otherwise affect any of the terms hereof. This Warrant is being executed as
an instrument under seal. The invalidity or unenforceability of any provision
hereof shall in no way affect the validity or enforceability of any other
provision.

     In witness whereof, the Company has caused this Warrant to be signed by an
officer thereunto duly authorized as of [______], 2000.

                                                SPECTRA SCIENCE CORPORATION

                                                By:
                                                   -----------------------------
                                                   Name:
                                                   Title:

Attest:

------------------------------
Name:
Title:

<PAGE>

                               NOTICE OF EXERCISE

        (To be Executed by the Registered Holder to Exercise the Warrant)

     The undersigned hereby irrevocably elects to exercise the right to purchase
                   shares of Common Stock, $.01 par value, of Spectra Science
------------------
Corporation, covered by Warrant No. WD(ii)-1 according to the conditions thereof
 and herewith makes payment of the Warrant Price of such shares in full.

     Specify method of exercise by check mark:

[_]  Such payment is hereby made in the amount of $______ by wire transfer or by
     certified or bank check.

[_]  The holder elects to receive shares for the value (as determined pursuant
     to Section 1.1 of the Warrant) of the Warrant.

                                 Printed Name
                                 of Warrant Holder:
                                                   -----------------------------

                                 Signature:
                                                   -----------------------------

                                 Title (if signing
                                 on behalf of a
                                 Warrant Holder):
                                                   -----------------------------

                                 Address:
                                                   -----------------------------

                                                   -----------------------------

                                                   -----------------------------

Dated:
      --------------------------

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