10 minutes maximum! Can you do it in 5?

1. Which of these diagrams correctly shows the path of a ray of light through a semi-circular plastic block? 2. Which of these statements best describes the path?

" As the ray enters the plastic from the air...

• A. .. it speeds up and bends away from the normal line".
• B. .. it speeds up and bends towards the normal line".
• C. .. it slows down and bends away from the normal line".
• D. .. it slows down and bends towards the normal line".

3+4: These questions are about refractive index:

3.Which of these formulas states "Snell's Law", used to show the relationship between the angle of incidence (i) and the angle of refraction (r)?

 a) n = sin i sin r

 b) n = sin r sin i

 c) r = sin n sin i

 d) i = sin n sin r

4. What is 'n' in this equation?

• A. The density of the substance.
• B. The speed of light in the substance.
• C. The refractive index of the substance.
• D. The volume of the substance.

5. The ray of light in question 1 has an angle of incidence of 400 and an angle of refraction of 250.

What is the value of 'n'?

• A. 1.52
• B. 0.66
• C. 0.03
• D. 1.60

6. Which of the following formulas correctly states the 'critical angle' formula?

 a) n = 1 c

 b) sin c = 1 n

 c) sin n = c 1

 d) sin n = 1 c

7-9: These questions are about total internal reflection in a prism:

7. Which of the following diagrams shows the path of a ray of light that has been totally internally reflected through a glass prism? 8. If the glass prism has a refractive index of 1.6, what is the critical angle of the glass?

• A. 390
• B. 420
• C. 450
• D. 490

9. The prism shown is a 450 prism, and light is totally internally reflected when it hits the surface at 450.

What is the minimum refractive index for a substance to be used in this prism?

• A. 1.0
• B. 1.4
• C. 1.5
• D. 1.6
10. Total internal reflection is used in long glass strands to carry light signals. These strands are called..

• A. Light cables.
• B. Optical fibres.
• C. Laser channels.
• D. EM wave cables.