Waves

Question 1

What is a wave?

Answer 1

A disturbance that transfers energy without transferring matter.

Question 2

What is wavelength (λ)?

Answer 2

The distance between two identical points on consecutive waves (e.g., crest to crest).

Question 3

What is amplitude?

Answer 3

The height of a wave from its rest position – indicates energy.

Question 4

What is frequency (f)?

Answer 4

The number of waves passing a point per second, measured in Hertz (Hz).

Question 5

What is wave period (T)?

Answer 5

The time taken for one complete wave to pass a point.

Question 6

What is the equation linking wave speed, frequency, and wavelength?

Answer 6

v = f λ

Where: v = Wave speed (m/s), f = Frequency (Hz), λ = Wavelength (m)

Question 7

Mnemonic for remembering the wave speed equation?

Answer 7

“Very Fast Lamborghini” → v = f λ

Question 8

What are the two types of waves?

Answer 8

Transverse and longitudinal.

Question 9

What is a transverse wave?

Answer 9

Oscillations are perpendicular to wave direction (e.g., light, water waves).

Question 10

What is a longitudinal wave?

Answer 10

Oscillations are parallel to wave direction (e.g., sound, seismic P-waves).

Question 11

Mnemonic to remember wave types?

Answer 11

“Light Travels, Sound Slides” → Light = Transverse, Sound = Longitudinal

Question 12

How can you measure wave speed for sound?

Answer 12

Echo method – Make a sound 50m from a wall, record time for echo, use: Speed = Distance / Time.

Question 13

How can you measure wave speed for water ripples?

Answer 13

Use a stroboscope to freeze wave motion, then measure wavelength and use v = f λ.

Question 14

What happens when a wave hits a boundary?

Answer 14

It can be reflected, absorbed, or transmitted (refracted).

Question 15

What is the law of reflection?

Answer 15

Angle of incidence = Angle of reflection.

Question 16

What is the difference between specular and diffuse reflection?

Answer 16

Specular – Smooth surface, clear reflection (e.g., mirror). Diffuse – Rough surface, scattered reflection.

Question 17

What is refraction?

Answer 17

Waves change direction when entering a different medium, due to a change in speed.

Question 18

What happens when light enters a denser material?

Answer 18

It slows down and bends toward the normal.

Question 19

Mnemonic to remember refraction?

Answer 19

“Fast Away, Slow Towards”

Question 20

How does sound travel?

Answer 20

As longitudinal waves, vibrating particles in a medium.

Question 21

Why can’t sound travel in space?

Answer 21

There are no particles to carry vibrations (no medium).

Question 22

How do we hear sound?

Answer 22

Sound waves cause the eardrum to vibrate. Vibrations are amplified by the small bones in the ear. The cochlea converts vibrations into electrical signals for the brain.

Question 23

What is ultrasound?

Answer 23

Sound waves above 20,000 Hz, beyond human hearing.

Question 24

What are two uses of ultrasound?

Answer 24

Medical imaging (e.g., pregnancy scans), Detecting flaws in materials.

Question 25

How does ultrasound imaging work?

Answer 25

Waves partially reflect at boundaries → Computer processes reflections to create an image.

Question 26

What type of wave are EM waves?

Answer 26

Transverse waves that travel at the speed of light in a vacuum.

Question 27

What are the seven types of EM waves (in order of increasing wavelength)?

Answer 27

Gamma, X-rays, UV, Visible Light, IR, Microwaves, Radio waves.

Question 28

Mnemonic for remembering EM waves?

Answer 28

"Good Xylophones Usually Vibrate In Musical Rhythm"

Question 29

Which EM waves are harmful and why?

Answer 29

UV → Skin cancer, eye damage. X-rays & Gamma rays → Ionising radiation, causes DNA mutations.

Question 30

How can radiation exposure be minimized?

Answer 30

Lead aprons (X-rays), Sunscreen (UV rays).

Question 31

What are the two types of lenses?

Answer 31

Convex (converging) and concave (diverging).

Question 32

What is a convex lens used for?

Answer 32

Magnifying glasses, cameras, telescopes.

Question 33

What is a concave lens used for?

Answer 33

Correcting short-sightedness.

Question 34

Mnemonic to remember lens types?

Answer 34

"Convex Collects, Concave Caves"

Question 35

What is black body radiation?

Answer 35

All objects emit & absorb radiation based on temperature.

Question 36

What happens as an object gets hotter?

Answer 36

It emits more radiation at shorter wavelengths (e.g., red-hot metal).

Question 37

What is the Doppler Effect?

Answer 37

A change in frequency of a wave due to motion of the source.

Question 38

What happens when a sound source moves toward you?

Answer 38

Higher frequency (pitch), shorter wavelength.

Question 39

What happens when a sound source moves away?

Answer 39

Lower frequency (pitch), longer wavelength.

Question 40

Mnemonic for Doppler Effect?

Answer 40

"Toward = Tighter, Away = Apart"