WORKSHEET-2

Refraction of Light at Plane Surfaces
Worksheet

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I. Fill in the blanks

1. At critical angle of incidence, the angle of refraction is _____

Ans: 90 °

2. ______________ phenomena of light takes place in optical fibres

Ans: Total internal reflection 

3. Sini/Sinr= _______

Ans: Constant

4. The refractive index of glass respect to air is 2. Then the critical angle of glass air

interface is _____

 Ans: 30 °

II. Answer the following questions 

5. In which case, the angle of incidence and the angle of refraction are same?

Ans: Light ray travels in normal direction 

6. Define Total Internal Reflection ?

 Ans: When the angle of incidence is greater than critical angle, the light ray reflected

 into denser medium at interface.This phenomenon is called total internal reflection.

7. Mirages are formed due to?

Ans: Total internal reflection. 

8. Write the applications of total internal reflection?

 Ans: Brilliance of diamond, optical fibres, formation of mirages

 

III. Read the passage and answer the following questions

Take a bright metal ball and make it black with soot in a candle flame. Immerse in

water.

9.How does it appear?

Ans: Shiny or Silvery 

10. Why it appears like that?

Ans: Due to total internal reflection 

1. Fill in the blanks 

1.Total internal reflection takes place when a light ray propagates from _______ to _____

Ans: Denser, Rarer 

2. Critical angle of diamond is________

Ans: 24.4 °

3. A bunch of thin fibres form a _________

Ans: light pipe 

4. During refraction, light follows ________ law

Ans: Snell’s 

II. Answer the following questions 

5.Determine the refractive index of benzene, if the critical angle is 420

Ans: Given C=42°

 n=1/sinC = 1/sin42°

 = 1/0.6691 = 1.49

6. Can you take a photo of a mirage?

Ans: Yes, I can take a photo of a mirage 

7. Why do stars appear twinkling?

Ans: Stars appear twinkling due to multiple refractions of light through different

atmospheric layers with different refractive indices.

8.What is the basic principle of endoscope?

Ans: Total internal reflection

9. Why do the straws appears to be in straight line, even though they are not in

straight line?

Ans: They are in normal direction