CAIE IGCSE Physics Dispersion of Light Question Bank

Practise prism dispersion through colour-dependent refraction, visible-spectrum order and monochromatic-light definitions using labelled ray diagrams.

Exam points

draw each colour refracting at both prism faces, with violet deviating more than red
explain dispersion through different speeds or refractive indices for different frequencies
order visible colours by wavelength or frequency and define monochromatic as one frequency

Covered syllabus points

3.2.4.1—Dispersion of light as illustrated by 3.2.4.2—Traditional seven colours of the 3.2.4.3—Recall that visible light of a single

[Maximum number: 4]

(a)

Fig. 6.1 shows white light incident at point X on a glass prism.

Fig. 6.1

[ 3 ]

(i)

From point X on Fig. 6.1, draw a ray of red light, labelled R and a ray of violet light, labelled V, to show how a spectrum is formed on the screen.

[ 2 ]

(ii)

State the colour of light in the visible spectrum with the shortest wavelength.

[ 1 ]

(b)

The critical angle for a type of glass is $42^{\circ}$ .

Fig. 6.2 and Fig. 6.3 show two prisms ABC and PQR made of this type of glass. A ray of monochromatic red light passes into each of the prisms.

Fig. 6.2

Fig. 6.3

[ 1 ]

(i)

State what is meant by monochromatic light.

[ 1 ]

[Maximum number: 1]

A ray of light is incident on a soap film. Fig. 5.1 shows a magnified image of a small part of the soap film. The ray of light is refracted as it enters the soap film.

Figure for Question 3.2.4 Dispersion of light question 2 — CAIE IGCSE Physics

soap film
```
air
```

The refractive index of the soap film is 1.28 .

The ray of light is monochromatic red light with a wavelength of 680 nm in air.

Define monochromatic.

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Covered syllabus points

3.2.4 Dispersion of light question 1

Question (a)

Question (i)

Question (ii)

Question (b)

Question (i)

3.2.4 Dispersion of light question 2