Problem: Upon exposure, the amount of light energy that reaches the film determines the effect upon the emulsion. If the brightness of the light is multiplied by a factor and the exposure of the film decreased by the same factor by varying the camera's shutter speed and aperture, so that the energy received is the same, the film will be developed to the same density. This rule is called reciprocity. The systems for determining the sensitivity for an emulsion are possible because reciprocity holds. In practice, reciprocity works reasonably well for normal photographic films for the range of exposures between 1/1000 second to 1/2 second. However, this relationship breaks down outside these limits, a phenomenon known as reciprocity failure.
How are ways of finding an emulsion's sensitivity possible?
The answer is the following: because reciprocity holds

Problem: Returning home to Brantford after six months abroad, Bell continued his experiments with his "harmonic telegraph".[N 12] The basic concept behind his device was that messages could be sent through a single wire if each message was transmitted at a different pitch, but work on both the transmitter and receiver was needed.
Where was Bell's home?
The answer is the following: Brantford

Problem: The standing wave forms with this desired pattern at the design frequency, f0, and antennas are normally designed to be this size. However, feeding that element with 3f0 (whose wavelength is 13 that of f0) will also lead to a standing wave pattern. Thus, an antenna element is also resonant when its length is 34 of a wavelength. This is true for all odd multiples of 14 wavelength. This allows some flexibility of design in terms of antenna lengths and feed points. Antennas used in such a fashion are known to be harmonically operated.
What can be added to f0 to create a standing wave pattern?
The answer is the following: 3f0

Problem: The climate of Florida is tempered somewhat by the fact that no part of the state is distant from the ocean. North of Lake Okeechobee, the prevalent climate is humid subtropical (Koppen: Cfa), while areas south of the lake (including the Florida Keys) have a true tropical climate (Koppen: Aw). Mean high temperatures for late July are primarily in the low 90s Fahrenheit (3234 C). Mean low temperatures for early to mid January range from the low 40s Fahrenheit (47 C) in northern Florida to above 60 F (16 C) from Miami on southward. With an average daily temperature of 70.7 F (21.5 C), it is the warmest state in the country.
The average daily temperature in Miami
The answer is the following:
With an average daily temperature of 70.7 F (21.5 C), it is the warmest state in the country