Pretend you are a teacher preparing a quiz for the text I will provide. 
            Each quiz question should follow the format below. 
            Ensure that you carefully recheck the questions and answers for accuracy. 
            The output should be a ready-to-use list of dictionaries for the Python eval function:

            [

                    "question": "WRITE THE QUESTION HERE",
                    "options": ["A) OPTION_1", "B) OPTION_2", "C) OPTION_3", "D) OPTION_4"],
                    "answer": INDEX_OF_CORRECT_ANSWER_IN_OPTIONS_LIST,
                    "explanation": "EXPLAIN WHY THE ANSWER IS CORRECT"

            ]

            Text:
             other and to the direction of propagation of the photon. 
Photons with shorter wavelength     have higher energy. 
C (velocity of light) = λ (wave length) x f (frequency). 
E (photon energy) = h (planks constant) x f (frequency). 


E    ,   f     ,  λ





Rontgen ray = X-ray:
Discovery of x radiation 
Selective penetration and differential absorption:
X-rays are differentially absorbed by Materials they pass through (they have a selective penetration and absorption power). 
More dense materials like an amalgam restoration will absorb more x-ray (called radioapaque: appear light/white) than less dense materials like skin tissue (called radiolucent: appear dark/black), this characteristic allows us to see images on x-ray film. 
X-ray production
X-rays are produced within the X-ray machine, also known as an X-ray tube. No external radioactive material is involved.
Radiographers can change the current and voltage settings on the X-ray machine in order to manipulate the properties of the X-ray beam produced. 
Different X-ray beam spectra are applied to different body parts. 
X-rays are generated via interactions of the accelerated electrons with electrons of tungsten nuclei within the tube anode. 
There are two types of X-ray generated: characteristic radiation and bremsstrahlung radiation. 
Direct and indirect action of radiation:
In direct action: the free electrons resulting from ionization interact with DNA molecule directly
In in- direct action: the free electrons resulting from ionization interact with water molecules inside the body and creates "free radicals". 

fluid mechanics
Fluid Mechanics (part 1: fluid static)
Density:
Definition: mass Density is the mass m of substances divided by its volume v.
ρ= m/v       [SI unit of mass density Kg/m3 ]
Example 1: (blood as a fraction of body weight)
 The body of man whose weight is 690N contain about 5.2 x 10-3 m3 of blood, (a) find the bloods weight. (b) express it as a percentage of a body weight.
Solution: (density of blood = 1060 Kg/m3) 
Bloods weight   W=mg= (ρv). g= (1060 x 5.2 x 10-3)x 9.8= 54 N
Percentage of bloods weight to the body weight   Percentage% = (54/690)x100= 7.8% 


Pressure:
Definition: Pressure is the force exerted on a surface per unit area.
P=F/A    SI unit is Pascal (1 Pa= 1 N/m2)     , [ in CGS : unit will be dyne/cm2]
Other units:  1atm= 1.013 x105 Pa= 760 mm Hg
                            1 torr = 1 mm Hg.
Example 2: estimate the force exerted on your eardrum due to the atmospheric pressure if the area of the eardrum is 10-4 m2.
Solution:
The atmospheric pressure P= 1 atm= 1.013x105 N/m2 (Pa)
The area = 10-4 m2
P=F/A                F=PXA= (1.013x105) X (10-4) = 10.13 N.



Manometer:
Used to : measure the pressure of a gas contained in a vessel is the open tube manometer.  
The gas presure P=P0 + ρgh [P is  absolute pressure].
So, the difference in pressure P- P0 = ρgh
P- P0  called  "gauge pressure" 



Surface Tension
A small insect resting on the surface of a po

            Quiz: