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Class 8 Science: Light: Mirrors and Lenses, 8 practice questions with answers

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These are 8 practice questions on the tenth chapter of the new NCERT Class 8 Science textbook, Curiosity, called Light: Mirrors and Lenses. Each has a short answer and the textbook page it comes from. They cover how mirrors are drawn in diagrams, two mirrors at a right angle, choosing a mirror for a job, the angles of reflection, the second law of reflection, lateral inversion, telling lenses apart, and where lenses are used. Try each question before you read the answer.

These questions are our own, drafted with AI help. Every fact was checked against the page it cites by a test script, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

What the chapter says you need

Facts from the NCERT textbook (Curiosity, Grade 8, Chapter 10, printed pages 152 to 169):

Mirrors

Question 1. In a diagram, a spherical mirror is drawn as a curved line, with shading on one side. (a) What does the shading show? (b) The shading is on the bulging (outer) side of the curve. Which kind of mirror is it? (c) Which kind is it if the shading is on the hollow (inner) side?

Answer: (a) the side that does not reflect; (b) concave; (c) convex. (a) In the drawings of spherical mirrors, the non-reflecting surface is shown shaded, so light is reflected from the other, unshaded side. (b) If the bulging side is shaded, the reflecting surface is the hollow side, which curves inwards: a concave mirror. (c) If the hollow side is shaded, the reflecting surface is the bulging side, which curves outwards: a convex mirror. (Concave and convex mirrors and how they are drawn, page 154.)

Question 2. Two plane mirrors meet at a right angle, one flat on a table and one standing upright at its edge. A ray strikes the flat mirror with an angle of incidence of 30°, and the reflected ray then goes on to strike the upright mirror. (a) What is the angle of reflection at the flat mirror? (b) What is the angle of incidence at the upright mirror?

Answer: (a) 30°; (b) 60°. (a) The angle of incidence equals the angle of reflection, so the ray leaves the flat mirror at 30° from its normal, which points straight up. (b) A ray 30° from the vertical is 90° − 30° = 60° from the horizontal. The upright mirror's normal is horizontal (at 90° to that mirror), so the ray meets it at 60° from the normal, and it is reflected at 60° too. (The law of reflection, page 158; working out the second angle from the right angle between the mirrors is our geometry, not the chapter's.)

Question 3. Which kind of mirror, concave or convex, is used for each job, and why? (a) The reflector behind a torch bulb. (b) A mirror at a sharp bend on a hill road. (c) The mirror a dentist uses to look at a tooth. (d) A mirror in a big shop to watch for theft.

Answer: (a) concave; (b) convex; (c) concave; (d) convex. (a) Reflectors of torches and of car and scooter headlights are concave. (b) A convex mirror curves outwards, so it shows a much wider area; at bends and crossings it lets drivers see traffic coming from the other side. (c) A dentist's mirror is concave: held close to a tooth, it gives an enlarged view. (d) A convex mirror lets one person watch a large area of a shop. (Uses of spherical mirrors, pages 156 and 157.)

Reflection

Question 4. A ray of light strikes a plane mirror, and the angle between the incident ray and the reflected ray is 70°. (a) What is the angle of incidence? (b) What is the angle of reflection? (c) Another ray makes an angle of 25° with the surface of a plane mirror. What is the angle between this ray and its reflected ray?

Answer: (a) 35°; (b) 35°; (c) 130°. The normal is the line at 90° to the mirror at the point where the ray strikes it, and it lies between the two rays. The angle of incidence (between the incident ray and the normal) equals the angle of reflection (between the reflected ray and the normal). (a) and (b): the two equal angles add up to 70°, so each is 70° ÷ 2 = 35°. (c) The normal makes 90° with the mirror, so a ray 25° from the surface is 90° − 25° = 65° from the normal. The angle of reflection is also 65°, so the angle between the two rays is 65° + 65° = 130°. (Angles of incidence and reflection, page 158.)

Question 5. A plane mirror lies flat on the floor of a room. A ray of light strikes it, and the incident ray lies in the flat surface of a wall that stands at right angles to the floor. (a) Where is the normal at the point where the ray hits the mirror? (b) In which plane must the reflected ray lie? (c) Does the second law of reflection still hold if the mirror is concave instead of plane?

Answer: (a) standing straight up from the mirror, in the wall's plane; (b) the plane of the wall; (c) yes, with the normal taken at the point where the ray strikes. (a) The normal is a line drawn at a right angle to the mirror, through the spot where the ray strikes it. The mirror is on the floor, so the normal stands straight up, and since the wall's plane contains that point and is upright, the normal lies in it too. (b) The second law of reflection says the incoming ray, the reflected ray and the normal where the ray meets the mirror are all in one flat plane. The incident ray and the normal are both in the wall's plane, so the reflected ray must be there as well. (c) Yes: the laws of reflection hold for plane, concave and convex mirrors alike. On a curved mirror, the normal is drawn at the exact point where the ray strikes, and the incident ray, that normal and the reflected ray lie in one plane. (The second law of reflection, page 159; the laws for all mirrors, page 160.)

Question 6. The word TOM is written on a card and held a little way in front of a convex mirror. (a) Will the image be upright or upside down, and larger or smaller than the card? (b) Will the letters read TOM, or will they be reversed left to right? (c) Would the left-right reversal also happen in a plane mirror and in a concave mirror?

Answer: (a) upright and smaller; (b) reversed left to right; (c) yes, in both. (a) A convex mirror always forms an erect image that is smaller than the object. (b) The image shows lateral inversion: left and right are swapped, so the word appears reversed and reads as a mirror-written MOT. (c) Yes: lateral inversion is seen in all three kinds of mirror, plane, concave and convex. (Images in spherical mirrors and lateral inversion, page 156.)

Lenses

Question 7. A lens is thinner in the middle than at its edges. (a) What kind of lens is it? (b) How will the letters of a book look through it, whatever its distance from the page? (c) Does it make a beam of parallel light come together or spread out?

Answer: (a) a concave lens; (b) erect and smaller; (c) spread out. (a) A lens that is thicker at the edges than in the middle is a concave lens; one thicker in the middle is a convex lens. (b) Seen through a concave lens, an object always appears erect and diminished, though its size changes as the lens is moved. (c) A concave lens diverges light, which is why it is also called a diverging lens. (Concave lenses, pages 163 and 164.)

Question 8. (a) What kind of lens is inside our eye, and what is special about it? (b) Name three things, other than a magnifying glass, that use lenses. (c) Why do we see things through a lens but in a mirror?

Answer: (a) a convex lens that can change its shape; (b) for example eyeglasses, cameras and microscopes; (c) a lens lets light pass through it, a mirror reflects it. (a) Inside the eye there is a convex lens. It can change its shape, which lets us read a book and also see something far away. (b) Eyeglasses, cameras (including phone cameras), telescopes and microscopes all use lenses. (c) Unlike mirrors, lenses let light pass through them, so we look through a lens at the object behind it. (Lenses and their uses, pages 163 and 165.)

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Sources

All opened and read on 2 November 2026. Page numbers are the printed page numbers of the textbook; printed page = PDF page + 151 for this chapter.

The facts are from the textbook pages above. The questions, answers and checks are our own. This guide is general information; follow your teacher and the textbook.