Laws of Reflection - UNSOLVED PRACTICE SET

Q7. State the two laws of reflection of light. Draw (or describe) a labelled diagram showing the incident ray, reflected ray, normal, and the angles.

Q8. Distinguish between regular (specular) reflection and diffuse (irregular) reflection. Give one real-life Indian example of each.

Q9. A ray of light strikes a plane mirror at 40° to the mirror surface. Find the angle of incidence, angle of reflection, and the angle between the incident and reflected rays.

Q10. Why can you see your face clearly in a calm lake but not in rippling water? Explain using the laws of reflection.

Q11. A light ray hits a mirror and reflects at 65°. By how many degrees must the mirror be rotated so that the reflected ray becomes perpendicular to the incident ray? Show reasoning.

Q12. Can the laws of reflection apply to sound? Give one practical example where sound obeys the same reflection principles as light.

Q13. State and explain the laws of reflection in detail. Include:
(a) precise definitions of angle of incidence and angle of reflection,
(b) the significance of the normal at the point of incidence,
(c) why all three — incident ray, normal, and reflected ray — must lie in the same plane,
(d) the distinction between regular and diffuse reflection with diagrams or descriptions, and
(e) two real-life applications of reflection of light.

Q14. Lateral inversion is a fascinating consequence of reflection from a plane mirror.
(a) Define lateral inversion.
(b) Explain why the letter 'A' looks the same in a mirror but the letter 'R' appears reversed.
(c) Give two practical situations in India where lateral inversion is deliberately used (e.g., AMBULANCE written on vehicles).
(d) Does lateral inversion occur in the vertical direction? Explain.
(e) If you raise your right hand in front of a mirror, which hand does the image appear to raise?

Q15. In a periscope used in submarines and tanks, two plane mirrors are placed at 45° angles.
(a) Trace the path of a ray of light through a simple periscope using the laws of reflection.
(b) How does the second mirror reinstate the original direction of the ray?
(c) What is the total deviation of the ray after both reflections?
(d) Why is 45° the optimal angle for the mirrors in a periscope?
(e) Name two other devices that use the principle of reflection of light from plane mirrors.

Q16. A ray of light hits a plane mirror at a point P. The angle between the incident ray and the reflected ray is 70°.
(a) Find the angle of incidence.
(b) Find the angle of reflection.
(c) If the mirror is now tilted by 15° (so the normal rotates by 15°), what is the new angle of incidence and angle of reflection?
(d) By how many degrees does the reflected ray rotate when the mirror is tilted by 15°?

Q17. Two plane mirrors are placed perpendicular to each other (at 90°). A ray of light strikes the first mirror at 30° to the normal.
(a) Find the angle of reflection from the first mirror.
(b) The reflected ray now hits the second mirror — find the angle of incidence on the second mirror.
(c) Find the angle of reflection from the second mirror.
(d) Show that the final reflected ray is parallel to the original incident ray. (Hint: angles in a triangle sum to 180°.)

Q18. The number of images formed between two mirrors at angle θ is n = (360/θ) − 1.
(a) Find the number of images when two mirrors are at 60°.
(b) At 45°.
(c) At 90°.
(d) At 0° (parallel mirrors) — what happens?
(e) Why do barbers use two facing mirrors to show a customer the back of their head?