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Light Trivia Quiz

This quiz is a series of questions on reflection, refraction, lenses and spectrum... basically, on different areas of light.

A multiple-choice quiz by Rossell. Estimated time: 6 mins.

Author
Rossell

Time
6 mins

Type
Multiple Choice

Quiz #
251,707

Updated
Dec 03 21

# Qns
10

Difficulty
Very Difficult

Avg Score
4 / 10

Plays
2950

One at a Time - Single Page - Timed Game

Question 1 of 10

1. A ray of white light strikes a rectangular glass block normally. How many rays of light, and what colour, emerge from the block? Hint

One ray of white light

Seven rays of light (VIBGYOR)

Three rays of red, blue and green light respectively

Impossible to say without knowing the composition of the polychromatic ray of light

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Question 2 of 10

2. A ray of light strikes a plane mirror and the angle of reflection is noted. The plane mirror is then rotated through an angle of 30 degrees, such that there is an increase in the angle of reflection.

If the initial angle of reflection was 15 degrees, what will be the new angle of reflection, after rotation? Hint

60 degrees

30 degrees

45 degrees

75 degrees

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Question 3 of 10

3. Which of the following prisms would be suitable for use in a periscope? Hint

An isosceles right angled prism

An equilateral prism

An isosceles prism

A prism with the following angles: 90 degrees, 42 degrees and 48 degrees

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Question 4 of 10

4. A specific mass of pure water is frozen to form completely transparent ice, in the shape of a lens. When forced underwater, the lens diverges light.

What is the shape of the lens? Hint

Convex lens

Cylindrical lens

Concave lens

Convexo-concave lens

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Question 5 of 10

5. Two monochromatic rays of light, one ray violet and the other red, travel from a vacuum into air. Their speeds change as a result.

What is the ratio of the speed of the violet ray to the speed of the red ray? Hint

1 : 1

3 : 1

2 : 1

1.5 : 1

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Question 6 of 10

6. Which of the following mirrors is most suitable for using as a reflector in car headlights? Hint

Parabolic mirror

Convex mirror

Concave mirror

Plane mirror

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Question 7 of 10

7. A person suffering from the ophthalmic disorder myopia is wearing spectacles with concave lenses. The transparent concave lenses are yellow in colour. This person looks at a picture of a yellow circle, a green square and a red triangle set against a blue background.

How does the picture appear to the person? Hint

It cannot be stated with certainty from the information given

Everything except for the circle looks black

Everything looks yellow.

Everything looks the same colour it is

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Question 8 of 10

8. [1/f= 1/v - 1/u] is the mirror formula, which enables us to evaluate the focal length of a concave mirror.

True

False

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Question 9 of 10

9. A camera is focused on a distant object. The distance between the lens and the photographic film is equal to 'f'.

The camera must now focus on a nearby object.

What will be the new distance between the photographic film and the lens? Hint

Exactly half of 'f'

Less than 'f'

More than 'f'

Equal to 'f' (no change)

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Question 10 of 10

10. An object is placed 10cm away from the lens of a camera. The image formed is the same size as the object.

What is the focal length of the lens of the camera? Hint

5 cm

20 cm

10 cm

Impossible to say

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Quiz Answer Key and Fun Facts

1. A ray of white light strikes a rectangular glass block normally. How many rays of light, and what colour, emerge from the block?

Answer: One ray of white light

Since the ray of white light strikes the glass surface normally and the angle of incidence will be zero, there will be no refraction of light and as a result, no separation of white light into its constituent rays.

2. A ray of light strikes a plane mirror and the angle of reflection is noted. The plane mirror is then rotated through an angle of 30 degrees, such that there is an increase in the angle of reflection. If the initial angle of reflection was 15 degrees, what will be the new angle of reflection, after rotation?

Answer: 75 degrees

"For a given incident ray, if a plane mirror is rotated through a certain angle, then the angle of reflection increases by twice that angle."

The plane mirror was rotated through 30 degrees, so the reflected ray will increase by (30 multiplied by 2)60 degrees.

3. Which of the following prisms would be suitable for use in a periscope?

Answer: An isosceles right angled prism

A refracting periscope uses isosceles right angled prisms as opposed to mirrors in a reflecting periscope. Refracting periscopes are based on the principle of total internal reflection.

4. A specific mass of pure water is frozen to form completely transparent ice, in the shape of a lens. When forced underwater, the lens diverges light. What is the shape of the lens?

Answer: Convex lens

Convex lenses converge light only when placed in a medium less dense than the material they are made of, otherwise they diverge light. The reverse happens with concave lenses. This is why it is inappropriate to designate lenses as 'converging' or 'diverging', as this property is subject to change.

Note: Water is denser than ice. Both are transparent.

5. Two monochromatic rays of light, one ray violet and the other red, travel from a vacuum into air. Their speeds change as a result. What is the ratio of the speed of the violet ray to the speed of the red ray?

Answer: 1 : 1

All colours of light have the same speed in air and vacuum.

6. Which of the following mirrors is most suitable for using as a reflector in car headlights?

Answer: Parabolic mirror

If a source of light is placed at the focal point of a concave mirror, a parallel beam of light is obtained after reflection.

However, a parabolic mirror has a greater aperture, and so if a light source is placed at the focus of a parabolic mirror, a larger beam of light is obtained and a larger area is illuminated.

Answer: It cannot be stated with certainty from the information given

Just like a light source appearing yellow can emit either monochromatic yellow light or a combination of various other wavelengths, for example red and green, any transparent material that is also yellow in colour, such as a yellow lens, might let not only yellow but also significant amounts of orange, green and red light to pass through while absorbing primarily in the blue spectrum.

Without knowing the absorption characteristics of the lens and the spectral characteristics of the light source, we can thus not conclude just how the picture will look.

8. [1/f= 1/v - 1/u] is the mirror formula, which enables us to evaluate the focal length of a concave mirror.

Answer: False

It is actually the lens formula. The mirror formula is [1/f= 1/v + 1/u].

9. A camera is focused on a distant object. The distance between the lens and the photographic film is equal to 'f'. The camera must now focus on a nearby object. What will be the new distance between the photographic film and the lens?

Answer: More than 'f'

For distant objects (placed beyond twice the focal length), the image is formed on the other side of the lens at the focus or within the focal length.

However, for nearby objects (placed between twice the focal length and the focal length), the image is formed on the other side of the lens, beyond the focus. As a result, for nearby objects, the distance between the lens and photographic plate will have to greater than that for distant objects.

Note: All camera lenses are convex.

10. An object is placed 10cm away from the lens of a camera. The image formed is the same size as the object. What is the focal length of the lens of the camera?

Answer: 5 cm

Let '2F' be a point on the principal axis of a convex lens that is located at twice the focal length of the lens.

An object is placed at 2F. Its image would be formed at 2F on the other side of the lens. The image would be real, inverted, and be the same size as the object.

Here, twice the focal length was equal to 10 centimetres. Therefore, the focal length of the lens is 5 centimetres.

Source: Author Rossell

This quiz was reviewed by FunTrivia editor crisw before going online.
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