Optics Practice Questions

Which lens, A or B, is a convex lens?

A beam of light rays travelling parallel to the principal axis is shone at lens A.

Describe what happens to these rays after they pass through the lens.

What is meant by the focal length of a lens?

Which lens, A or B, can never produce a real image?

The glass used in a bathroom window is translucent.

What is meant by translucent?

A tomato is an opaque object. In white light the tomato appears red.

Explain why.

A lump of coal appears black in white light.

Explain why.

Which surface, A or B, shows diffuse reflection?

Explain, in terms of the surface, why the reflected rays from this surface travel in the directions shown.

Name one surface that would produce specular reflection.

A projector uses a convex lens to produce an image of a slide on a screen.

The slide is $3.5\ \mathrm{cm}$ tall. The image on the screen is $1.4\ \mathrm{m}$ tall.

Calculate the magnification produced by the projector lens.

A camera lens produces an image of a flower with a magnification of $0.25$

The image of the flower is $4.5\ \mathrm{mm}$ tall.

Calculate the height of the flower.

Give your answer in mm.

Explain why magnification has no units.

Complete Figure 3 to show how the image of the object is formed by the lens.

Use an arrow to represent the image.

The image is upside down. Give two other words that describe the image.

The object is now moved so that it is $5.0\ \mathrm{cm}$ from the lens.

State and explain what happens to the size of the image.

Complete the sentence.

A colour filter works by absorbing some wavelengths of light and ______________ other wavelengths.

Explain why the yellow background of the poster appears black when it is viewed through the blue filter.

The student now holds a red filter in front of the blue filter and looks at a white lamp through both filters.

Explain what the student sees.

Use Figure 4 to determine the height of the image.

Calculate the magnification produced by the lens.

Use Figure 4 to give one piece of evidence that the image formed is a real image.

Complete Table 1 to describe the image formed when the object is $15\ \mathrm{cm}$ from the lens and when the object is $5\ \mathrm{cm}$ from the lens.

Use words from the list below. You may use each word more than once.

real virtual upright inverted magnified diminished

State where an object must be placed for a convex lens to be used as a magnifying glass.

Which colour of visible light has the longest wavelength?

A beam contains only blue light and green light.

Which of these two colours has the higher frequency?

Green light has a wavelength of $5.2 \times 10^{-7}\ \mathrm{m}$.

The speed of light in air is $3.0 \times 10^{8}\ \mathrm{m/s}$.

Calculate the frequency of this green light.

Use the equation:

$\text{wave speed} = \text{frequency} \times \text{wavelength}$

Complete Figure 5 to show how an image of the object is formed by the concave lens.

Use an arrow to represent the image.

The image is upright. Give two other words that describe the image.

On the completed diagram the image is $1.0\ \mathrm{cm}$ tall.

Calculate the magnification produced by the lens.

Complete Figure 6 to show how the image of the stamp is formed.

Use an arrow to represent the image.

The image formed is magnified. Give two other words that describe the image.

On the completed diagram the image of the stamp is $6.0\ \mathrm{cm}$ tall.

Calculate the magnification produced by the magnifying glass.

Light from car headlights hitting the sign is reflected by diffuse reflection.

Explain why diffuse reflection is useful for a road sign.

In white light the background of the sign appears white and the border appears red.

Explain, in terms of wavelengths of light, why the background and the border appear these colours.

At night the sign is lit by a street lamp that emits only a narrow band of yellow light.

Describe and explain the appearance of the sign under this street lamp.