# IGCSE Physics Paper-1: Specimen Questions with Answers 80 - 82 of 149

## Question 80

### Question

MCQ▾

Find correct statement about speed of electromagnetic waves in a vacuum.

### Choices

Choice (4)

a.

Infra-red waves have the greatest speed.

b.

Ultra-violet waves have the greatest speed.

c.

All electromagnetic waves have the same speed.

d.

Visible light waves have the greatest speed.

c.

### Explanation

Speed of the all electromagnetic waves in a vacuum is same. Because speed of electromagnetic waves are not depending upon wavelength. And there is no electric and magnetic effect present in vacuum.

## Question 81

### Question

MCQ▾

Find time between shouting and hearing the echo if boy is on an island 300 m away and shouts for help. He hears reply as echo from some cliffs. Consider sound travels at 200 m/s through the air.

Choice (4)

a.

b.

c.

d.

b.

### Explanation

Distance between boy and cliff is 300 m, and he shouted for help but its voice back as echo. So distance travel by voice is 2 ⨯ 300

And the sound travels with speed 200 m/s

## Question 82

### Question

MCQ▾

Thumb is placed on bicycle outlet. If air is pushed in what change will occur to pressure and volume?

### Choices

Choice (4)

a.

Pressure decreases, volume decreases

b.

Pressure decreases, volume remains the same

c.

Pressure increases, volume remains the same

d.

Pressure increases, volume decreases