Refraction through a Glass Slab - UNSOLVED PRACTICE SET

Q7. What happens to a ray of light when it passes through a glass slab? Describe the path of the ray from entry to exit.

Q8. Define lateral shift (lateral displacement). On what factors does it depend? Write the formula: d = t × sin(i − r) / cos r.

Q9. Prove that the emergent ray from a glass slab is parallel to the incident ray. Use Snell's Law at both surfaces.

Q10. Why does a glass slab not produce an inverted image like a prism does? Explain in terms of the geometry of the two surfaces.

Q11. You look at a line on paper through a thick glass slab. The line appears shifted sideways. Explain this observation using the concept of lateral displacement.

Q12. A ray enters a glass slab (n = 1.5) at 45°. Find the angle of refraction at the first surface. Then find the angle of refraction at the second surface (glass to air). What do you observe about the emergent angle?

Q13. Describe the refraction of light through a glass slab in detail. Your answer must include:
(a) what happens at the first air-glass surface (direction of bending and reason),
(b) what happens inside the glass slab,
(c) what happens at the second glass-air surface,
(d) why the emergent ray is parallel to the incident ray (prove using Snell's Law at both surfaces), and
(e) define lateral displacement and explain what causes it.

Q14. A glass slab of thickness 6 cm and refractive index 1.5 is placed on a table. A light ray strikes the first surface at 60°.
(a) Find the angle of refraction in glass.
(b) Prove that the emergent ray is parallel to the incident ray.
(c) Find the lateral shift using d = t sin(i−r)/cos r.
(d) If the thickness is doubled to 12 cm, what happens to the lateral shift?
(e) Would the lateral shift be zero if the ray entered perpendicularly (i = 0°)? Explain. (sin 60° = 0.866, use appropriate inverse trig.)

Q15. Explain the practical consequences of refraction through a glass slab in real-life Indian situations:
(a) Why does the bottom of a glass of water appear raised (shallower) when viewed from above?
(b) Why does a fish seen through the glass wall of an aquarium appear shifted from its actual position?
(c) A driver looks at the road through a thick windshield — does the glass slab effect cause any optical distortion?
(d) In camera lenses, multiple glass elements are stacked — how does each element introduce lateral shift and how is this corrected in lens design?
(e) What is the difference between a glass slab and a glass prism in terms of the path of the emergent ray?

Q16. A ray of light strikes a glass slab (n = 1.5) at 45°. (sin 45° = 0.707, sin 30° = 0.5.)
(a) Find the angle of refraction at the first surface.
(b) Verify the emergent angle equals 45° using Snell's Law at the second surface.
(c) If the slab is 4 cm thick, find the lateral displacement. (d = t sin(i−r)/cos r, where i−r = 45°−30° = 15°, sin 15° ≈ 0.259, cos 30° ≈ 0.866)

Q17. A goldfish in an aquarium is 12 cm from the glass side wall. The glass wall has n = 1.5 and thickness 1 cm. A child looks at the fish through the glass.
(a) Using apparent depth formula (apparent depth = real depth / n), find where the fish appears to be inside the water.
(b) The glass slab introduces an additional lateral shift. Would the combined effect make the fish appear closer or farther?
(c) Why can you still easily locate the fish despite these optical effects? 

Q18. A glass slab of refractive index 1.6 and thickness 8 cm is placed in the path of a ray of light. The angle of incidence is 50°. (sin 50° = 0.766.)
(a) Find the angle of refraction in glass.
(b) Find the lateral shift using d = t sin(i−r)/cos r.
(c) If the refractive index is increased to 2.0 (keeping thickness and angle the same), would the lateral shift increase or decrease? Explain using the formula. (sin of new refraction angle ≈ 0.383, angle ≈ 22.5°)