Waves
Transverse and Longitudinal waves:
• Waves are vibrations that transfer energy from place to place without matter being transformed.
• Transverse waves are when the displacement is at right angles to the direction of the wave. (e.g. all
electromagnetic waves, ripples in water, a wave on a string)
• Longitudinal waves are when the displacement is parallel to the wave direction (e.g. sound waves, shock
waves).
• The wavelength of any wave is the distance between two matching points on neighbouring waves. The
symbol used to represent wavelength is 𝜆.
• The amplitude of any wave is the maximum distance a point moves from its rest position.
• The amplitude of a transverse wave is the height of a part or trough from the wave’s rest position of
the wave.
• The larger the amplitude, greater the energy of the wave.
• The frequency is the number of waves passing any point each second.
!"#$%& () *+,%- .+-/ + .(0!/
• 𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 = /0#%
• Frequency is measured in Hertz (Hz)
#
• 𝑊𝑎𝑣𝑒 𝑠𝑝𝑒𝑒𝑑 2 - 3 = 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 (𝐻𝑧) × 𝑤𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡ℎ(𝑚)
• The time period is the time taken for each wave to pass a fixed point.
1
• 𝑇𝑖𝑚𝑒 𝑝𝑒𝑟𝑖𝑜𝑑 (𝑠) = 2&%3"%!45 (78)
Measuring the speed of sound outside:
• When outside, the echoes from a tall building can be used to measure the speed of sound in air.
• Stand 40m in front of a tall building and bang two blocks of wood together.
• Each time you hear an echo, bang the blocks together again.
• Have another student use a stopwatch to time how long it took to hear 10 echoes.
Reflection:
1. Place the plane mirror on a piece of paper.
2. Draw a line across the front of the mirror
3. Draw a normal to the mirror
4. Shine rays of light at varying angles to the normal and record the position of the incident and
reflected rays
5. Measure the incident angles and the reflected angles for each ray. Record your results in a table.
• Angles are the same, Angle of incidence = angle of reflection
Refraction:
• When light moves from one material it bends, this is called refraction.
• It does this because it changes speed as it passes between the boundary of the materials.
• The ray of light is refracted towards the normal when it goes into a glass block. The ray of light is
refracted away from the normal when it comes out of a glass block. The ray coming out of the glass
block is parallel to the ray going into the block.
Transverse and Longitudinal waves:
• Waves are vibrations that transfer energy from place to place without matter being transformed.
• Transverse waves are when the displacement is at right angles to the direction of the wave. (e.g. all
electromagnetic waves, ripples in water, a wave on a string)
• Longitudinal waves are when the displacement is parallel to the wave direction (e.g. sound waves, shock
waves).
• The wavelength of any wave is the distance between two matching points on neighbouring waves. The
symbol used to represent wavelength is 𝜆.
• The amplitude of any wave is the maximum distance a point moves from its rest position.
• The amplitude of a transverse wave is the height of a part or trough from the wave’s rest position of
the wave.
• The larger the amplitude, greater the energy of the wave.
• The frequency is the number of waves passing any point each second.
!"#$%& () *+,%- .+-/ + .(0!/
• 𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 = /0#%
• Frequency is measured in Hertz (Hz)
#
• 𝑊𝑎𝑣𝑒 𝑠𝑝𝑒𝑒𝑑 2 - 3 = 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 (𝐻𝑧) × 𝑤𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡ℎ(𝑚)
• The time period is the time taken for each wave to pass a fixed point.
1
• 𝑇𝑖𝑚𝑒 𝑝𝑒𝑟𝑖𝑜𝑑 (𝑠) = 2&%3"%!45 (78)
Measuring the speed of sound outside:
• When outside, the echoes from a tall building can be used to measure the speed of sound in air.
• Stand 40m in front of a tall building and bang two blocks of wood together.
• Each time you hear an echo, bang the blocks together again.
• Have another student use a stopwatch to time how long it took to hear 10 echoes.
Reflection:
1. Place the plane mirror on a piece of paper.
2. Draw a line across the front of the mirror
3. Draw a normal to the mirror
4. Shine rays of light at varying angles to the normal and record the position of the incident and
reflected rays
5. Measure the incident angles and the reflected angles for each ray. Record your results in a table.
• Angles are the same, Angle of incidence = angle of reflection
Refraction:
• When light moves from one material it bends, this is called refraction.
• It does this because it changes speed as it passes between the boundary of the materials.
• The ray of light is refracted towards the normal when it goes into a glass block. The ray of light is
refracted away from the normal when it comes out of a glass block. The ray coming out of the glass
block is parallel to the ray going into the block.
