Physical Science - Chapter Optics - Answer the questions

This paper is the project required for a under graduate student in topic " optics" of subject physical science . The required paper work a reference are provided for the students.

Speed of light (c) = 3.0 x 10 exp (8) m/s  

1- Define the following:  

Ans : Reflection - Reflection is the shift in course of a wavefront at a point of interaction between two unique media so the wavefront gets back to the medium from which it started. Normal models incorporate the reflection of light, sound, and water waves.  

Refraction - refraction is the shift in direction of a wave passing from one medium and then onto the next or from a steady change in the medium. Refraction of light is the most generally noticed peculiarity, however different waves, for example, sound waves and water waves also experience refraction.  

2- What is the speed of light in glass if you know that the Speed of light in vacuum is (c) = 3.0x108 m/s and the refractive index of glass is 1.52?

Ans : Given that,

         Refractive Index of Glass = 1.52

         Speed of Light, c = 3 x 10⁸ m/s

         We know that

         N_g = c / V_g

         V_g = c / N_g

         V_g = 3 x 10⁸  / 1.52

         V_g = 1.97 x 10⁸ m/s

Where V_g = Speed of Light through glass

            N_g = Refractive Index of Glass  

3- Why do you see a broken pencil if it is immersed in a glass of water? 

Ans :  The pencil was seen to be bent when it is kept in a glass of water due to the refraction of light. The refraction of light takes place when the speed of light varies when it travels from one medium to the  another. Due to the result immersed portion of the pencil appears to be bent when viewed at an angle from the outside. 

What is the abbreviation ROYGBIV stand for? Give the name of each letter in this abbreviation.

Ans :  ROYGBIV is an abbreviation for the succession of tints usually depicted as making up a rainbow.  Each letter in the abbreviation stands for Red, Orange, Yellow, Green , Blue, Indigo, Violet.   

4- Define Wavelength, and Frequency:
Ans : Wavelength can be defined as the distance between the two consecutive crests or troughs in a wave. In a high-frequency wave, the distance between the crests and troughs is less than in a low-frequency wave.

The term frequency means the number of times a wave vibrates when it passes through a medium. Frequency is measured as the total number of oscillations in unit time.

What are the two different types of waves (give one example)  

Ans : The two types of waves are longitudinal and transverse waves. Longitudinal waves consist of alternating compressions and rarefractions in a medium. An example of longitudinal wave is sound wave. Transverse waves are those with the surface going up and down. The high point of a transverse wave is called the crest and low point is called the trough. An example is waves those on water.  

What are the two types of optics?
Ans :  In Physics optics is the study of light and the phenomena associated with it. As light has dual nature, that is it can be considered as wave or particle, Generally there are two types of optics.

1.      Physical Optics – It deals with the study of light when considering the wave nature of light

2.      Geometric Optics – It deals with the study of light when light is considered as particle and studies are based on the concept of light rays , providing a geometric model for light.  

5- What is refractive index? Explain why diamond is more expensive than graphite? Give at least two reasons.

Ans : In optics, the refractive index of a material is a dimensionless number that depicts how quickly light travels through the material.

It is defined as  n= c/v

Where c is the speed of light in vacuum

            v is the  velocity of light in the medium

            n is the refractive index of the medium

Diamond is more expensive than Graphite. Graphite is the most stable form of carbon at room temperature and pressure and it is available in plenty. Whereas diamonds are metastable phase of Carbon , So it has to be mined. Diamonds can be cut, polished and shaped into gemstones. It’s high refractive index allows it to reflect more light and It is one among the hardest known material. Due to these reasons diamonds are more expensive than graphite even both are made of Carbon. 
6- Explain the two different types of lenses in details and draw an example of each showing the rays diagrams with the focal points.

 Ans : Two different  types of lenses are

·         Convex lens

·         Concave lens

Convex lenses are thicker in the center and more slender at the edges. A concave lens is more flat in the center and thicker at the edges. A convex lens is also called as converging lens as the light beams twist inwards and join at a point which is known as the focal length. Then again, the concave lens is otherwise called a diverging lens since it twists the equal light beams outward and separates them at the point of convergence. 

7- What kind of lenses exist (have been found) inside the human eyes?

 Ans : The lens in the human eye is a clear construction that focuses light entering the eye on the retina. The lens is biconvex and ellipsoid in structure. It has been adjusted outward on the two sides. The light beams entering the eye are calibrated and converged at a single point on the retina.

 8- Circle the correct statements: there may be more than one correct statement 

a) Converging (or convex) lenses are thicker at the center than the edges

b) Converging (or convex) lenses are thicker at the edges than the center

c) Diverging (or concave) lenses are thicker at the center than the edges

d) Diverging (or concave) lenses are thicker at the edges than the center

e) None of the above

 

9- Circle the correct statements: there is only one correct statement

 

a) Electrons and protons have the same charge (value and sign) but different mass

b) Electrons and protons have the same charge and the same mass

c) Neutrons and protons have the same charge but different mass

d) Electrons and Neutrons have the same charge but different mass

e) None of the above

 

10- If your favorite radio station is on the FM Dial at100 MHz (Mega Hertz) Calculate the wave length for this Radio station. Hint use the equation c = Lf, Where L is the wavelength and c is given at the top of the exam.

Ans : Given that 

          Frequency, f  = 100 MHz = 100 x 10⁶  Hz (s^-1)

          Wavelength , L = c/f

          L = (3 x 10⁸) / (100 x 10⁶ )

          L = 3 m

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