Light | CIE IGCSE Physics: Co-ordinated Sciences (Double Award) Topic Questions 2023

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1a3 marks

A student is determining the refractive index n of the material of a transparent block.

Fig. 3.1 shows the outline ABCD of the transparent block.

(i)

On Fig. 3.1:

- draw a normal NL at the centre of side AB
- continue the normal so that it passes through side CD of the block
- label the point F where NL crosses AB
- label the point G where NL crosses CD.

[1]

(ii)

Draw a line EF at an angle i = 30° to the left of the normal and above side AB.

[1]

(iii)

Mark the positions of two pins P₁ and P₂ on line EF placed at a suitable distance apart for this type of ray-tracing experiment.

[1]

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1b4 marks

The student observes the images of P₁ and P₂ through side CD of the block so that the images of P₁ and P₂ appear one behind the other.

He places two pins P₃ and P₄ between his eye and the block so that P₃, P₄ and the images of P₁ and P₂ seen through the block, appear one behind the other.

The positions of P₃ and P₄ are marked on Fig. 3.1.

(i)

- Draw a line joining the positions of P₃ and P₄. Continue the line until it meets the normal NL.
- Label the point H where the line meets side CD. Draw the line FH.

[1]

(ii)

Measure and record the length a of the line GH.

a = ........................................................ [1]

(iii)

Measure and record the length b of the line FH.

b = ........................................................ [1]

(iv)

Calculate the refractive index n using the following equation:

n = \frac{0.5 b}{a}

n = ........................................................ [1]

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1c1 mark

Extended tier only

The student repeats the procedure using the angle of incidence i = 45°.

a = 3.2 cm

b = 6.9 cm

Calculate the refractive index n, using the equation $n = \frac{0.71 b}{a}$ .

n = ........................................................

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1d2 marks

The student expected the two values of refractive index n obtained in this experiment to be equal.

State two difficulties with this type of experiment that could explain any difference in the two values of n.

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1e1 mark

A student suggests precautions to take in this experiment to obtain reliable results.
Tick one box to indicate the most sensible suggestion.

$□$ Carry out the experiment in a darkened room.

$□$ Use pins that are taller than the height of the block.

$□$ View the bases of the pins.

□

View the pins with one eye closed.

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2a1 mark

A student investigates the position of the image in a plane mirror.

ray-diagram
Fig. 3.1 shows the ray-trace sheet he uses.

The student draws the line MR.

• He draws a normal NL to this line that passes through the centre of MR.

• He labels the point at which NL crosses MR with the letter B.

• He draws a line from B at an angle of incidence i = 30° to the normal below MR and to the left of the normal. He labels the end of this line A.

• He places a pin P₁ on line AB, as shown in Fig. 3.1. He places another pin P₂ on the line AB.

• He places the reflecting face of the mirror vertically on the line MR.

• He views the images of pins P₁ and P₂ from the direction indicated by the eye in Fig. 3.1.

(i)

On Fig. 3.1, mark with a cross a suitable position for pin P₂ in this experiment.

[1]

(ii)

He places two pins P₃ and P₄ some distance apart so that pin P₃ and the images of P₂ and P₁ all appear exactly behind pin P₄. The positions of P₃ and P₄ are shown on Fig. 3.1.

Draw the line joining the positions of P₃ and P₄. Continue the line until it extends at least 7.0 cm beyond MR.

[2]

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2b3 marks

The student keeps pin P₁ in the same position but moves pin P₂ so that the angle of incidence i = 40°.

The pin positions P₅ and P₆ for the reflected ray are marked on Fig. 3.1.

(i)

Draw the line joining the positions of P₅ and P₆. Continue the line until it extends at least 7.0 cm beyond MR.

Label with the letter Y the point where the two lines cross beyond MR.

[1]

(ii)

Draw a line from P₁ to MR that meets MR at a right angle. Measure and record the length a of this line.

a = ..................................................... [1]

(iii)

Draw a line from the point labelled Y to MR that meets MR at a right angle. Measure and record the length b of this line.

b = ..................................................... [1]

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2c2 marks

The student removes all the pins. He places pin P₇ on the normal at a distance 6.0 cm from the front of the mirror.

He views the image of P₇ in the mirror.
He places pin P₈ on the normal behind the mirror.
He adjusts the position of P₈ so that the image of the bottom of the pin P₇ and the top of pin P₈ seen over the mirror appear as one pin when viewed from all angles in front of the mirror.

(i)

On Fig. 3.1, measure the distance x along the normal between P₈ and the mirror.

x = ..................................................... [1]

(ii)

Complete the diagram in Fig. 3.2 to show the appearance of the image of pin P₇ and pin P₈ as described in (c).

[1]

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2d2 marks

The student expects the readings to show that the image formed in a plane mirror is the same distance behind the mirror as the object is in front of the mirror. Readings of a = b and x = 6.0 cm will show this.

State whether your readings show that the image formed in a plane mirror is the same distance behind the mirror as the object is in front of the mirror. Justify your statement by reference to the readings.

statement:

justification:

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2e1 mark

The student carries out this experiment with care. Suggest a practical reason why the results may not be accurate.

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Light (CIE IGCSE Physics: Co-ordinated Sciences (Double Award))

Topic Questions