Analysing Refraction of Waves By Ms Nurul Ain Mat Aron

describe refraction of waves in terms of the angle of incidence, angle of refraction, wavelength, frequency, speed and direction of propagation draw a diagram to show refraction of waves

Objectives

Refraction of Waves

Water waves travel from deep region to shallow region

Sound waves travel through air of different densities

Light waves travel through medium air of different optical densities

Refractions occurs when:

Refraction of Water Waves

When water waves travel through regions of different depths, the speed changes and the waves are refracted.

Direction of wave

Shallow region

Deep region

Refraction of Plane Water Waves

Refraction is defined as the change in the direction of travel of the waves caused by the change in the speed of the waves as they pass through different media.

Direction of wave

Refraction of Water Waves

When water waves which pass through are perpendicular to the boundary of the shallow region, the direction of wave travel is not changed but refraction occurs.

λ λ λ

Deep water Deep water Shallow water

Refraction of Water Waves

When water waves travels from a region of deep water to a region of shallow water, refraction occurs.

Characteristics of Refraction

λ1 λ2

v1 v2

Deep water Shallow water

Refraction of Water Waves

When water waves travels from a region of deep water to a region of shallow water, refraction occurs.

Characteristics of Refraction

Region Deep water region

Shallow water region

Wave speed Faster Slower

Wavelength Longer Shorter

frequency unchanged unchanged

Applications of Refraction

The effect of refraction causes the wavefronts in the sea to follow the shape of the coastline as the water becomes shallower.

Shoreline-shaped Wavefronts

Applications of Refraction Shoreline-shaped Wavefronts

In the centre of the ocean, the water waves travel at uniform speed as the depth of the sea

water is uniform

Hence, the wavefronts are straight and parallel to each other.

Applications of Refraction Shoreline-shaped Wavefronts

When the waves reach the coast, the water is shallower . Wave speed is reduced and the refraction occurs. The wavefronts are refracted and becomes closer to each other.

Refraction causes the wavefronts to be bent towards the normal and this results in the wavefronts following the shape of the coastline.

Applications of Refraction

Sound waves travel faster in warm air than in cool air.

Warm Day and Cold Night

On a hot day, the hot surface of the earth causes the layer of air near the surface to be warmer.

This causes sound waves to be refracted away from the Earth.

Applications of Refraction

The opposite effect takes place on a cool night.

Warm Day and Cold Night

The sound waves travel slower in the cooler layer of air near the surface of the Earth than in upper, warmer air.

As s result, the waves are refracted towards the Earth

This explains why sound can be heard over a linger distance on cold night compared with a hot day.

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