Light: Shadows and Reflections Part 3: MCQs (Q51–Q75)
Part 3 — Plane Mirror Images & Ray Diagrams (Questions 51–75)
51. The image formed by a plane mirror is always:
A. Real, inverted and smaller.
B. Virtual, erect and of same size. — Correct answer: B
C. Real and magnified.
D. Absent; only shadows form.
Explanations:
A/C/D) Incorrect.
B) Correct — standard properties of plane mirror images.
52. A ray of light strikes a plane mirror at 40° to the surface (not normal). The angle with the normal is:
A. 50°.
B. 40° — Correct answer: B
C. 90°.
D. 0°.
Explanations:
If ray makes 40° with surface, then with normal (perpendicular to surface) it makes 50° — check geometry. Wait — be careful: if angle with surface = 40°, angle with normal = 90-40 = 50°. Need correct.
Correction: Let’s re-evaluate. The question: “A ray strikes plane mirror at 40° to the surface (not normal). The angle with the normal is:” Right answer should be 50°. So correct answer A. I must ensure correctness.
I’ll produce accordingly.
Rewriting Q51? But we are at Q52. Update:
Corrected Q52:
Let’s present properly.
52. A ray of light strikes a plane mirror at 40° to the surface (i.e., measured from the surface). What is its angle of incidence measured from the normal?
A. 40°
B. 50° — Correct answer: B
C. 90°
D. 0°
Explanations:
A) Incorrect — angle with normal is complementary to angle with surface.
B) Correct — normal is perpendicular, so angle with normal = 90° − 40° = 50°.
C/D) Incorrect.
53. To locate the image of an object in a plane mirror using ray diagrams, you must extend:
A. The incident rays forward beyond mirror.
B. The reflected rays backward behind the mirror until they meet. — Correct answer: B
C. The normal only.
D. The mirror itself.
Explanations:
A) Incident rays don’t intersect behind mirror; reflected rays appear to come from behind — incorrect.
B) Correct — virtual image is at intersection of backward extensions of reflected rays.
C/D) Incorrect.
54. A student stands 1.5 m from a plane mirror. The student will see:
A. Only the top half.
B. Full body if mirror is at least 0.75 m tall, properly placed. — Correct answer: B
C. Nothing.
D. Image twice the height.
Explanations:
A/C/D) Incorrect.
B) Correct — minimum mirror height to see full body is half your height placed appropriately.
55. A plane mirror gives an image that is:
A. Closer to the mirror than the object.
B. Same distance behind mirror as object is in front. — Correct answer: B
C. Always farther than object.
D. Tangible and can be touched behind mirror.
Explanations:
A/C/D) Incorrect.
B) Correct — image distance equals object distance.
56. Which pair of rays is enough to locate image in plane mirror?
A. Two reflected rays and their backward extensions. Correct answer: A
B. Two incident rays only (without reflection).
C. One random ray only.
D. No rays — guess only.
Explanations:
A) Correct — trace two rays, reflect them using law, then extend reflected rays back to intersect behind mirror.
B/C/D) Incorrect.
57. A plane mirror produces lateral inversion because:
A. It turns top into bottom.
B. It reverses the component of position perpendicular to the mirror plane (left-right as perceived). — Correct answer: B
C. It makes objects transparent.
D. It bends light into colors.
Explanations:
A/C/D) Incorrect.
B) Correct — mirror flips depth axis producing perceived left-right swap.
58. If a candle is placed in front of a plane mirror and moved closer, the image will:
A. Move away from mirror on same side.
B. Also move closer behind the mirror at same distance as candle from mirror. — Correct answer: B
C. Become real.
D. Disappear.
Explanations:
A) Image stays behind mirror, distance equals object distance, so moves accordingly — B is correct.
C/D) Incorrect.
59. In a periscope, the two mirrors are set at:
A. 0° to each other.
B. 45° to the tube so light is reflected down/up the tube. — Correct answer: B
C. 90° to the tube only.
D. Random angles.
Explanations:
A/C/D) Incorrect.
B) Correct — periscope uses mirrors at 45° to change direction of light by 90°.
60. When two plane mirrors are inclined at 60°, the number of images formed of an object placed between them is given by formula (360/θ − 1) if 360/θ is integer. For θ = 60°, number of images:
A. 5
B. (360/60 − 1) = 5 images — Correct answer: B
C. 6
D. 0
Explanations:
A) B is explanation; same.
B) Correct — 360/60 = 6 ; 6−1 = 5 images.
C/D) Incorrect.
61. If you look at two mirrors at 90° with a coin between them, how many reflections of coin do you see?
A. One.
B. Three — Correct answer: B
C. Ten.
D. None.
Explanations:
A/C/D) Incorrect.
B) Correct — two single reflections + one double reflection → typically three images.
62. A plane mirror produces a virtual image because:
A. The reflected rays physically meet behind the mirror.
B. The backward extensions of reflected rays appear to meet behind the mirror, but actual rays do not. — Correct answer: B
C. Mirror emits light.
D. The image is luminous.
Explanations:
A) Reflected rays do not actually meet behind mirror — incorrect.
B) Correct — makes image appear behind mirror (virtual).
C/D) Incorrect.
63. Which ray is NOT used to construct image in plane mirror diagrams?
A. Ray hitting mirror and reflecting at equal angle.
B. Ray incident at normal (reflects back).
C. Ray refracted through mirror. — Correct answer: C
D. Ray whose reflection is extended backward.
Explanations:
A/B/D) Valid rays in reflection diagrams — incorrect to choose.
C) Correct — refraction does not occur through an opaque reflective mirror.
64. For a plane mirror, magnification (image height / object height) is:
A. 0
B. 1 (unit magnification) — Correct answer: B
C. >1 always
D. <0
Explanations:
A/C/D) Incorrect.
B) Correct — plane mirror produces image same size as object (magnification = +1).
65. If a ray strikes a plane mirror at 30° to the normal, the reflected ray will make with the mirror surface an angle of:
A. 30°
B. 60° Correct answer: B
C. 0°
D. 90°
Explanations:
Angle with mirror surface = 90° minus angle with normal. If angle with normal is 30° then angle with surface = 60°. Reflection has same angle with normal, so with surface it’s 60°. Thus B correct.
A/C/D) Incorrect.
66. Which of the following is required to produce a clear image in a plane mirror?
A. Mirror must be curved.
B. Mirror surface must be smooth and polished. — Correct answer: B
C. Mirror must be transparent.
D. Mirror must be very hot.
Explanations:
A) Curvature changes image; not required for plane mirror.
B) Correct — smooth polished surface gives specular reflection and clear image.
C/D) Incorrect.
67. Which effect causes a mirror image to appear reversed left to right but not top to bottom?
A. Gravity.
B. Our interpretation of front-back reversal due to mirror flipping the depth axis. — Correct answer: B
C. Mirror rotates the object physically.
D. Mirror erases colors.
Explanations:
A/C/D) Incorrect.
B) Correct — mirror reverses depth axis; perceived left-right swap is due to how humans interpret facing someone vs. mirror.
68. A plane mirror is moved towards a fixed object by 10 cm. The image moves:
A. 5 cm toward the object.
B. 10 cm toward the object (behind mirror), so relative separation between object and image reduces by 20 cm. — Correct answer: B
C. Away from object.
D. Vanishes.
Explanations:
A) Incorrect.
B) Correct — image distance equals object distance; so moving mirror closer by 10 cm reduces both object-to-mirror and image-to-mirror distances by 10 cm; separation reduces by 20 cm overall.
C/D) Incorrect.
69. If a small mirror is held at chest height, what minimum fraction of your height must the mirror be to see your entire body?
A. One-quarter of your height.
B. One-half of your height. — Correct answer: B
C. Equal to your height.
D. None.
Explanations:
A) Too small.
B) Correct — half height mirror suffices when placed properly.
C/D) Incorrect.
70. Which device uses reflection to allow people to see around corners or over obstacles?
A. Periscope. Correct answer: A
B. Kaleidoscope.
C. Microscope.
D. Telescope.
Explanations:
A) Correct — periscope uses mirrors at 45° to view from different vantage points.
B/C/D) Incorrect.
71. A mirror placed on a wall reflects a ray such that incident angle = 30°. What is the angle between incident ray and reflected ray?
A. 30°.
B. 60°. — Correct answer: B
C. 90°.
D. 0°.
Explanations:
If angle with normal = 30°, reflected ray angle with normal = 30°, so angle between incident and reflected = 30° + 30° = 60°. B correct.
72. If a plane mirror produces a virtual image 3 m behind the mirror, the object is:
A. 6 m in front of mirror.
B. 3 m in front of mirror. — Correct answer: B
C. 1.5 m in front.
D. Invisible.
Explanations:
Image distance = object distance for plane mirror. Hence object is 3 m in front. B correct.
73. A mirror that spreads out light rays (diverges) is:
A. Concave mirror.
B. Convex mirror. — Correct answer: B
C. Plane mirror only.
D. Pin-hole.
Explanations:
A) Concave converges (can focus) — incorrect.
B) Correct — convex mirror diverges rays giving virtual diminished image.
C/D) Incorrect.
74. Two plane mirrors make an angle of 120°. The number of images formed of an object between them will be:
A. 2.
B. (360/120 − 1) = 2 — Correct answer: B
C. 3.
D. Infinite.
Explanations:
360/120 = 3 -> 3−1 = 2 images. B correct.
75. In which case will you see three images in two mirrors? (Choose best)
A. When mirrors are parallel.
B. When mirrors are at 60° to each other. Correct answer: B
C. When mirrors are perpendicular.
D. When mirrors are curved.
Explanations:
A) Parallel gives infinite images — incorrect.
B) Correct — at 60°, formula yields 5 images? Actually 360/60 = 6 → 5 images, but three images arises at 90°? Wait — we earlier had 90° → 3 images. This question ambiguous. Need to avoid inconsistency.
We already used 60° earlier (#60) with 5 images. #75 must be corrected: For three images, angle = 90°. So correct answer should be C.