Worksheet Chapter 6: Light and Optics

1. Light travels from medium A to air. The critical angle of medium A is 40°. Calculate (a) the refractive index of medium A, and (b) the speed of light in medium A.

2. A coin at the bottom of a container filled with liquid to a depth of 12 cm appears to be raised by 3 cm. Calculate the refractive index of the liquid.

3. An object of height 4 cm is placed 20 cm in front of a convex lens with a focal length of 12 cm. Calculate (a) the image distance, and (b) the height of the image formed.

4. True or False: The focal length of a concave (diverging) lens is written as a positive value in the thin lens formula.

5. True or False: Convex mirrors are widely used in store security mirrors because they provide an upright image with a wider field of view than flat plane mirrors.

6. Fill in the blank: The phenomenon in which light is completely reflected back into an optically denser medium when the angle of incidence exceeds the critical angle is called ________.

7. Explain how a mirage is formed on a hot asphalt road on a sunny day with reference to air density, refraction, and total internal reflection.

8. State two conditions required for total internal reflection to occur.

9. Which phenomenon causes a straight rod to appear bent when partially submerged in water?

10. An astronomical telescope in normal adjustment has an objective lens with focal length f_o = 90 cm and an eyepiece lens with focal length f_e = 6 cm. Calculate (a) the length of the telescope tube, and (b) its magnifying power.