Light: Mirrors and Lenses

In Activity 10.1, Riya looks at her face in the outer side of a shiny metallic spoon, which bulges outwards. How does her image look?

1. aErect but smaller than her face
2. bInverted and larger than her face
3. cInverted and smaller than her face
4. dErect and of the same size as her face

The reflectors of torches and of the headlights of cars and scooters are:

1. aflat, like a plane mirror
2. bmade of convex lenses
3. cconvex in shape
4. dconcave in shape

A curved piece of glass is given a thin reflective coating of aluminium on its outer curved surface. What does it become?

1. aA plane mirror
2. bA convex mirror
3. cA concave mirror
4. dA concave lens

Why does the side-view mirror of a car show the driver a much wider area of the road behind?

1. aIt is a concave mirror, curved inwards.
2. bIt is a convex mirror, curved outwards.
3. cIt is a plane mirror fixed at an angle.
4. dIt is a convex lens that lets light pass through it.

In the study of reflection, the angle of reflection is the angle between the:

1. areflected ray and the mirror
2. breflected ray and the normal
3. cincident ray and the normal
4. dincident ray and the reflected ray

A lens which is thicker at the middle than at the edges is called a:

1. aconcave lens
2. bconcave mirror
3. cconvex lens
4. dconvex mirror

In Activity 10.8, a small drop of water is placed on an oiled glass strip held over printed text. The letters just below the drop may look larger than the letters nearby. Why?

1. aThe drop's surface curves outwards, so it acts like a simple lens.
2. bThe drop's surface is flat, like a window pane.
3. cThe oil reflects the letters like a plane mirror.
4. dThe drop's surface curves inwards, so it acts like a concave mirror.

A concave mirror and a convex mirror lie on a table with their reflecting surfaces facing upwards. As in Activity 10.2, how can you tell which one is the concave mirror?

1. aLook straight down from above: the one that shows your image is the concave mirror.
2. bView them from the side at eye level: the one whose reflecting surface curves outwards is concave.
3. cWeigh them: the heavier one is the concave mirror.
4. dView them from the side at eye level: the one whose reflecting surface curves inwards is concave.

An object is moved slowly away from a convex mirror. What happens to its image?

1. aIt becomes inverted and keeps getting smaller.
2. bIt stays erect and becomes larger than the object.
3. cIt stays erect and smaller than the object, and becomes slightly smaller.
4. dIt becomes inverted and larger than the object.

In Activity 10.6, several parallel beams of light are made to fall on a convex mirror. What happens to the reflected beams?

1. aThey spread apart (diverge).
2. bThey come closer together (converge).
3. cThey stay parallel to one another.
4. dThey pass through the mirror.

According to the chapter, which of these groups contains only things that use lenses to work?

1. aTorch reflectors, cameras and side-view mirrors
2. bDental mirrors, microscopes and road safety mirrors
3. cHeadlight reflectors, telescopes and surveillance mirrors
4. dCameras, microscopes and eyeglasses

In a museum, Asha starts far away from a large concave mirror and walks slowly towards it until she is very close. What does she see?

1. aHer erect image keeps getting smaller.
2. bHer inverted image keeps getting larger and, very close to the mirror, becomes erect and enlarged.
3. cHer erect image keeps getting larger all the way.
4. dHer inverted image keeps getting smaller.

Assertion (A): In Activity 10.5, the reflected beam disappears from the extended part of the sheet when that part is bent along the edge of the table.

Reason (R): The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

Assertion (A): A shiny metallic spoon can act as a mirror.

Reason (R): Spherical mirrors are made by grinding and polishing a flat glass piece into a curved surface.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

Assertion (A): An object seen through a concave lens always appears erect.

Reason (R): An object seen through a concave lens always appears enlarged.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

Assertion (A): Lateral inversion is seen only in the images formed by plane mirrors.

Reason (R): A plane mirror always forms an erect image of the same size as the object.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

1. I. I. Mirrors whose reflecting surfaces are spherical are called spherical mirrors.
2. II. II. A spherical mirror can be thought of as a part of an imaginary hollow sphere.
3. III. III. In the drawn representation of a spherical mirror, the reflecting surface is shown shaded.

Which of the statements above about spherical mirrors are correct?

1. aOnly I and III
2. bOnly II and III
3. cOnly I and II
4. dI, II and III

1. I. I. Rays are straight lines with arrows that show the path along which light travels.
2. II. II. The normal is a line drawn at \(90^\circ\) to the mirror at the point of incidence.
3. III. III. The ray of light that comes back from the mirror is called the reflected ray.

Which of the statements above about drawing reflection are correct?

1. aOnly I and II
2. bI, II and III
3. cOnly I and III
4. dOnly II and III

1. I. I. A lens is a piece of transparent material, usually glass or plastic, which has curved surfaces.
2. II. II. Looking through a flat glass window pane makes objects look larger.
3. III. III. Unlike mirrors, lenses allow light to pass through them.

Which of the statements above about lenses are correct?

1. aOnly I and III
2. bOnly II and III
3. cOnly I and II
4. dI, II and III

1. I. I. More than 800 years ago, in the time of Bhāskara II, astronomers observed reflected images of stars and planets in shallow bowls of water.
2. II. II. The laws of reflection are clearly written down in the literature of that period.
3. III. III. Devices that concentrate sunlight into a small area using mirrors and lenses are called solar concentrators.

Which of the statements above are correct?

1. aOnly I and II
2. bI, II and III
3. cOnly II and III
4. dOnly I and III

Match each item in List I with what it is in List II:

1. a(i)-Q, (ii)-S, (iii)-P, (iv)-R
2. b(i)-Q, (ii)-S, (iii)-R, (iv)-P
3. c(i)-S, (ii)-Q, (iii)-P, (iv)-R
4. d(i)-S, (ii)-Q, (iii)-R, (iv)-P

Match each object in List I with what it does to a parallel beam of light in List II:

1. a(i)-Q, (ii)-R, (iii)-S, (iv)-P
2. b(i)-S, (ii)-Q, (iii)-R, (iv)-P
3. c(i)-Q, (ii)-S, (iii)-R, (iv)-P
4. d(i)-S, (ii)-Q, (iii)-P, (iv)-R

Match each item used in the chapter's activities with its purpose:

1. a(i)-Q, (ii)-S, (iii)-R, (iv)-P
2. b(i)-S, (ii)-Q, (iii)-R, (iv)-P
3. c(i)-Q, (ii)-S, (iii)-P, (iv)-R
4. d(i)-S, (ii)-Q, (iii)-P, (iv)-R

Riya wants to repeat Activity 10.11, holding a convex lens in sunlight to make a bright spot on a piece of paper. Which is the safe way to do it?

1. aLook at the Sun through the lens to find the brightest spot.
2. bFocus the bright spot on a friend's palm to feel how hot it gets.
3. cDo it alone, without telling an adult, so that nobody disturbs the spot.
4. dFocus the light only on the paper, with an adult watching, and never look at the Sun through the lens.

Ritu holds a convex lens just above a page of her book and sees the letters erect and enlarged. She then slowly raises the lens higher and higher above the page while still looking through it. What will she notice?

1. aThe letters soon look inverted; at first they are enlarged, and later they become smaller.
2. bThe letters stay erect and keep getting larger.
3. cThe letters stay erect and become smaller than their real size.
4. dThe letters look exactly the same size and shape as they really are.

During a camp, Neha wants to reflect the beam of her torch from a plane mirror straight back towards herself, along the same path. How should the beam fall on the mirror?

1. aAt an angle of incidence of \(90^\circ\), grazing along the mirror
2. bAt an angle of incidence of \(45^\circ\)
3. cAlong the normal, so that the angle of incidence is \(0^\circ\)
4. dAt any angle, since a plane mirror always sends light back along its path

What is the angle of incidence in Ishaan's measurement?

1. a\(60^\circ\)
2. b\(90^\circ\)
3. c\(120^\circ\)
4. d\(30^\circ\)

What is the angle between the incident ray and the reflected ray in Ishaan's drawing?

1. a\(30^\circ\)
2. b\(60^\circ\)
3. c\(120^\circ\)
4. d\(90^\circ\)

Why does the newspaper begin to give out smoke?

1. aThe concave mirror lets sunlight pass through it, and the glass itself becomes hot.
2. bThe concave mirror spreads the sunlight evenly over the whole sheet, slowly warming all of it.
3. cThe concave mirror concentrates the reflected sunlight at one point, producing enough heat there to ignite the paper.
4. dThe concave mirror produces heat of its own whenever it is held facing the Sun.

Which is the correct reply to Kabir's remark?

1. aKabir is right: only plane mirrors follow the laws of reflection.
2. bKabir is wrong: the concave mirror lets sunlight pass through it and come together, as a convex lens does.
3. cKabir is right: a concave mirror makes the angle of reflection larger than the angle of incidence.
4. dKabir is wrong: each ray still follows the laws of reflection, and it is the curved surface that makes the reflected rays converge.