Waves

Question 1

What are longitudinal waves?

Answer 1

• sound waves and seismic P waves.
• particles in the material the sounds is travelling through move back and forth along the same direction the sound is travelling in.

Question 2

What are transverse waves?

Answer 2

• waves on the water surface, seismic S waves and electromagnetic waves.
• the particles of water move in a direction at right angles to the direction the wave is travelling in.
• move across the direction the wave is travelling.

Question 3

What happens to waves at a boundary?

Answer 3

Either:
-reflected
-refracted
-absorbed
-transmitted

Question 4

How do sound waves travel in air of different densities?

Answer 4

They travel slower in cooler, denser air than in warmer, less dense air.

Question 5

How do water waves travel in different depths?

Answer 5

Water waves travel faster in deep water than in shallow water. They can also change direction.

Question 6

How does the speed of light change when entering a different medium?

Answer 6

They slow down and change direction when they pass from air to glass.

Question 7

How can you investigate waves in fluids?

Answer 7

Aim:
To investigate the suitability of apparatus to measure the speed, frequency and wavelength of waves in a fluid.
Apparatus:
Ripple tank, motor, plane wave generator, stroboscope, ruler, A3 paper and pencil.
Steps:
1. Set up the apparatus
2. Calculate the frequency by counting the waves that pass a point in a second. Do this for a minute and then divide by 60 to get a more accurate value.
3. Use a stroboscope to freeze the waves and find the wave lengths. Project the waves onto an A3 piece of paper under the tank.
4. Calculate the wave speed.

Question 8

What’s the order of the electromagnetic spectrum?

Answer 8

Radio, Micro, Infrared, visible, ultraviolet, x-rays and gamma rays.
This is from longest to shortest wavelength and small to high frequency.

Question 9

All electromagnetic waves are…..

Answer 9

• transverse waves
• travel at the same speed
  ( 3 x 10 to the power of 8 ) in a vacuum.
• transfer energy to the observer.

Question 10

What is the behaviour of EM waves?

Answer 10

They may be:
1. Reflected off a surface.
2. Refracted when they move from one surface to another.
3. Transmitted when they move through a material.
4. Absorbed by different materials.

Question 11

What are the uses of EM waves?

Answer 11

Radio=
Communication, satellite transmissions and radio systems.
Micro=
Cooking, communication and satellite communications.
Infrared=
Thermal imaging cameras, electrical heaters and short range communications (remote controls).
Ultraviolet=
Used on bank notes to detect forgeries and used for disinfecting water.
X-rays=
Internal imaging and airport security scanners.
Gamma rays=
Sterilising equipment, detection of cancer and treatment of cancer.

Question 12

What are the dangers of the EM waves?

Answer 12

Gamma + X-rays=
Can cause mutations to the DNA in cells in the body. This may kill the cells or cause cancer.

Ultraviolet=
Can damage the skin causing sun burn and could cause cancer in the future.

Infrared=
To much infrared can cause skin burns.

Microwaves=
Can heat the water inside our bodies which could damage or kill cells.