Topic 4 -Waves

Question 1

What are waves

Answer 1

waves transfer energy without transferring matter

Question 2

The Two types of waves

Answer 2

Longitudinal and transverse waves

Question 3

Longitudinal waves and examples

Answer 3

Longitudinal waves have vibrations that are parallel to the direction the wave is travelling e.g. sound, seismic and P-waves

Question 4

Transverse waves and examples

Answer 4

Transverse waves have vibrations perpendicular to the direction the wave is travelling e.g. all E.M. waves

Question 5

Wave speed equation

Answer 5

wave speed (m/s) = distance/ time 
or wavelength (m) x frequency (Hz)

Question 6

Electromagnetic waves

Answer 6

They are all transverse waves and transfer energy
there are seven different types
Eyes can only detect a small part of this spectrum
-visible light

Question 7

Electromagnetic spectrum order and frequency

Answer 7

(left to right)

• Radio waves (long wavelength and low frequency- least dangerous)
• Microwaves
• Infrared
• Visible light
• Ultra violet
• X-rays
• Gamma rays ( short wavelength, high frequency - most dangerous )

Question 8

What is refraction?

Answer 8

The waves travel at different speeds - when a wave hits a boundary between two materials at an angle it changes direction – if hits at the normal, changes speed but not refracted
- speed & wavelength decrease

Question 9

What is ultrasound ?

Answer 9

• a sound with frequencies higher than 20,000

Question 10

What is ultrasound used for ?

Answer 10

• medical imaging like scanning a fetus

- Industrial imaging e.g. finding flaws in materials

Question 11

What is a period

Answer 11

• time taken for wave to completely pass single point

- inversely proportional to frequency

Question 12

Frequency definition (Hz)

Answer 12

• number of waves to pass single point per second

Question 13

Wave front definition

Answer 13

• direction of wave

Question 14

What is Reflection

Answer 14

• reflect off of flat surfaces – smoother surface, stronger reflected wave

Question 15

What is transmission ?

Answer 15

• Waves pass through transparent material
• more transparent, more light will pass through material
• can refract

Question 16

What is absorption ?

Answer 16

• frequency of light matches energy levels of the electrons
• light will be absorbed by the electrons and not re-emitted

Question 17

How sound waves travel through ear

Answer 17

• outer ear channels wave down ear canal
• • hits ear drum, eardrum vibrates at same frequency as sound wave ( small bones connected vibrate too)
• • vibrations of bones transferred to cochlea – turned to fluid & move to compression waves
• • small hairs on cochlea move –when a frequency is received, hair attuned to that frequency moves a lot, releasing an electrical impulse to the brain, interpreted as sound

Question 18

What is infra sound ?

Answer 18

• sound wave w/ frequency less than 20 Hz ( aka seismic waves
• 2 types P- waves & S-waves

Question 19

What is infra sound used for?

Answer 19

• used to explore earth’s core