4.1 Waves and vibrations

Question 1

Define electromagnetic waves

Answer 1

an electric and magnetic wave packet or photon that can travel through free space

Question 2

What are the 7 sections in the electromagnetic wave spectrum in order?

Answer 2

radio waves
microwaves
infrared radiation
visible light
ultraviolet radiation
X-rays
gamma radiation

Question 3

Define longitudinal waves

Give 3 examples

Answer 3

waves with a direction of vibration parallel to the direction of prorogation of the waves
e.g sound waves, primary seismic waves, ultrasound

Question 4

Define transverse waves

Give 3 examples

Answer 4

waves with a direction of vibration perpendicular to the direction of propagation of the waves
e.g electromagnetic waves, secondary seismic waves, ripples on water/waves on a string

Question 5

Define plane-polarised

Answer 5

transverse waves that vibrate in one plane only

Question 6

Define unpolarised

Answer 6

Transverse waves with vibrations that change from one plane to another

Question 7

Why can’t longitudinal waves be polarised?

Answer 7

Because the direction of vibration and direction of propagation are the same.

Question 8

Give an example of how polarisation is used in daily life and how.

Answer 8

Polaroid sunglasses reduce the glare of light reflected by water or glass. The reflected light is polarised and the intensity is reduced when it passes through the polaroid sunglasses.

Question 9

Explain what happens when 2 polaroid filters are placed perpendicular to each other.

Answer 9

The polarised light from the 1st filter cannot pass through the second filter as the alignment of molecules in the 2nd filter is at 90 degrees to the alignment in the 1st filter.