Light

a. An image that cannot be obtained on a screen is called virtual image.

Explanation: There are two types of images which can be formed: real images and virtual images. Real images are the images which can be obtained on a screen whereas virtual images can’t be obtained on a screen.

b. Image formed by a convex mirror is always virtual and smaller in size.

Explanation: Convex mirrors always form a virtual image which means that the image can’t be obtained on the screen and also the image is small in size i.e. diminished and upright image of an object.

c. An image formed by a plane mirror is always of the same size as that of the object.

Explanation: Plane mirrors forms the same size of the image as that of object.

d. An image which can be obtained on a screen is called a real image.

Explanation: There are two types of images which can be formed: real images and virtual images. Real images are the images which can be obtained on a screen whereas virtual images can’t be obtained on a screen.

e. An image formed by a concave lens cannot be obtained on a screen.

Explanation: Concave lens always forms a virtual image and a virtual image can’t be obtained on screen.

a. F

A convex mirror forms a virtual, erect and diminished image. So, we can’t obtain an enlarged image by a convex mirror.

b. T

The concave lens forms a virtual image which is erect and diminished. So, it is True.

c. T

The image obtained using a concave mirror can be real or virtual, enlarged and inverted. The image formed depends on the distance of object from the concave mirror.

d. F

Real images are the images which can be obtained on screen and virtual images are those which can’t be obtained on the screen. So, this statement is false.

e. F

Both real and virtual images can be obtained with the help of a concave mirror. The image formation depends on the distance of object from the mirror. So, this statement is false.

The correct match is: a : v.

A plane mirror forms an erect image and the size of the image is same as that of the size of the object.

B : ii.

Since a convex mirror forms a virtual, diminished and upright image. Due to which it covers a large area of field of view. That’s why a convex mirror can form image of objects spread over a large area.

C : i.

A convex lens is used as a magnifying glass because it forms a magnified image of an object.

D: iii.

A concave mirror is used by dentists to see enlarged image of teeth because a concave mirror forms an enlarged image of the teeth and is helpful for the dentist.

E:vi.

A concave lens forms a virtual, erect and diminished image i.e. smaller in size as that of object.

The characteristics of image formed by a plane mirror are as follows:

1. Image is formed behind the mirror.

2. The image is erect, inverted and has the same size as that of the object.

3. The distance of the image from the mirror is equal to the distance of the object from the mirror.

The following picture shows the image formation by plane mirrors:

Since the image formed by a plane mirror is erect and inverted. Moreover, these letters are vertically symmetric. So, the image of following letters appears exactly same as the object: A, H, I, M, O, T, U, V, W ,X, Y. For example see the picture below:

Virtual images are the images which can’t be obtained on a screen.

The image formed in case of plane mirror is virtual and can’t be obtained on the screen.

The following picture shows the virtual image formed by plane mirror:

The differences between a convex lens and a concave lens are as follows:

1. Concave lens is thinner from middle and thicker from edges but convex lens is thick from middle and thinner from edges.

2. Convex lens converges the light rays which falls on it and forms a real image whereas a concave lens diverges the light rays falling on it and forms virtual images.

Concave mirrors are used by dentists to see the enlarged images of teeth because a concave mirror forms an enlarged image of the teeth and is helpful for the dentist.

Convex mirrors are used in automobiles in rear view mirror. It helps to view the objects spread over a large area behind the driver.

Concave mirror forms a real image of an object and can be obtained on the screen. However, the nature of image formed depends on the distance of object from the mirror.

A virtual image is formed by a concave lens. A concave lens forms a virtual, erect and diminished image i.e. smaller in size as that of object.

The correct answer is: option ii.

The image obtained using a concave mirror can be real or virtual, enlarged and inverted. The image formed depends on the distance of object from the concave mirror. Convex mirror and concave lens forms virtual image but the image obtained is not enlarged, instead it is diminished and the image formed by plane mirror is same size as that of object.

The correct answer is: option (iii)

Since a plane mirror is being used in the above problem and a plane mirror the distance between the object and mirror is equal to the distance between image formed and the mirror.

Distance between mirror and image of David = 4m

When David moved 1m towards the mirror, then distance becomes = 3m

Distance of object from the mirror = distance of image from the mirror = 3m

Distance between David and his image = 3m +3m = 6m

The correct answer is: option iii.

Since the speed of the car = 2m/s, so the distance between the car and the truck will decrease at double rate as the image of truck travels a distance twice the distance by car. So, the speed at which the image of the truck appears to approach the driver = 4m/s.