Junior Secondary · Science

Images formed by convex lenses: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Images formed by convex lenses.

10 questions22 marksFree, no account

Question 1

1 mark

What happens to a parallel beam of light rays after passing through a convex lens?

Question 2

1 mark

An object is moved slowly towards a convex lens from a very far distance until it reaches the principal focus (\(F\)). Which of the following correctly describes the change in the real image formed on a screen?

Question 3

1 mark

When constructing a ray diagram for a convex lens, a student draws a ray that originates from the top of the object and passes through the focal point \( F \) on the same side as the object before it hits the lens. How will this ray travel after passing through the lens?

Question 4

1 mark

The distance between the optical centre of a convex lens and its focal point is called the:

Question 5

1 mark

A convex lens has a focal length of \( 15\ \text{cm} \). If an object is placed at a distance of \( 40\ \text{cm} \) from the optical centre of the lens, what are the characteristics of the image formed?

Question 6

2 marks

If a student successfully projects a clear image of a candle flame onto a white wall using a single convex lens, what are the two essential characteristics of this image?

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Question 7

3 marks

In a ray diagram for a convex lens, a light ray enters the lens parallel to the principal axis. Describe the path of this ray after it passes through the lens and explain why this occurs.

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Question 8

5 marks

A student uses a convex lens to view a small insect. As she moves the lens closer to the insect (within the focal length), describe the change in the size and position of the virtual image observed.

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Question 9

3 marks

A ray box is used to send light rays through a convex lens. Describe the behavior of the following three light rays:

(a) A ray that enters the lens parallel to the principal axis. (1 point)

(b) A ray that passes through the optical centre of the lens. (1 point)

(c) A ray that passes through the principal focus (\(F\)) before hitting the lens. (1 point)

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Question 10

4 marks

A convex lens is often used in instruments like projectors and cameras because of its ability to converge light rays and form real images. Consider a convex lens with a focal length (\(f\)) of \(5\text{ cm}\).

(a) If an object is placed \(12\text{ cm}\) away from the lens, describe the four main characteristics of the image formed (nature, position relative to \(F\) or \(2F\), orientation, and size relative to the object).

(b) If the lens is used to project a sharp, real image of the object onto a screen, briefly explain, using the concept of light rays, why the image must be real to be visible on the screen.

(c) If the top half of this convex lens is covered completely with an opaque material, how will the brightness and completeness of the image formed on the screen change? Explain your reasoning.

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