Waves
What type of wave is light?
(mechanica l/ electromagnetic / transverse / longitudinal)
electromagnetic // transverse
State the law of reflection
Angle of incidence = angle of reflection (i = r)
which colour has the longest wavelength
red
what are the units used for velocity?
m/s
meters per second
what property relates to
1. pitch
2. loudness
frequency
amplitude
Using the term "oscillate" and "energy", what's the main difference between a transverse and longitudinal wave?
- the direction of oscillations and energy flow
Transverse = oscillations of particles are at right angles to the direction of the enrgy
Longitudinal = oscillations of particles are parallel to the direction of the energy
What happens to light when it passes from air to glass?
- does it speed up / slow down
- bend away / towards normal?
Light will slow down and bend toward the normal
what happens to the frequency as move from radio waves to gamma rays
it increases
f = v/λ
will sounds travel faster on a hot or cold day? why?
hot day, more kinetic energy, particles moving faster, higher rate of collision
They need particles (a medium) to transfer energy
Define the terms translucent, transparent, and opaque
Transparent - Almost all light is transmitted through the substance. E.g. glass
Translucent - Some light is transmitted, the rest is reflected or scattered. E.g. frosted glass
Opaque - No light is transmitted. Light is reflected or absorbed. E.g wood
Describe using the terms reflect and absorb, why we see only the colour blue in some objects
blue wavelength is reflected into our eyes, all other colour wavelengths are absorbed
A sound wave travels at 340 m/s. If the wavelength is 0.85 m, what’s the frequency
400 Hz
- stay the same
- we changed the loudness, not the pitch
Two waves travel across the same medium. Wave A has twice the frequency of Wave B, but they travel at the same speed.
- Which wave has the shorter wavelength, and why?
Wave A has the shorter wavelength because v = f × λ. If speed is constant, increasing frequency means wavelength must decrease
What does a convex lens do to light rays
Converges them to a focal point
If a green light was shining onto a red object, what colour would the object appear? Explain why.
- A red object reflects red light and absorbs most other colours
- When only green light is shining, there’s no red light to reflect.
- Since the red object absorbs the green light instead of reflecting it, it will look black/dark to our eyes
A student claims, “If you change the medium, the frequency of the wave will change too.” Using the wave equation, explain why this is incorrect
The frequency of a wave is determined by the source, not the medium. When the medium changes, the speed changes, so the wavelength adjusts, but the frequency remains constant.
Does sound travel faster in air, water, or steel? Explain why using particle theory
-Steel (particles closest)
- can transfer wave to next particle quicker as they are closer together
List all 4 wave properties, their symbol, and what they are measured in
wavelength, lambda, meters
frequency, Hz, Hertz
period, T, seconds
amplitude, A, meters
List the two types of reflection and define them.
Regular reflection - Light reflects off smooth surface à clear image
diffuse reflection -Rough surfaces reflect and scatter light in many directions
White light passes through a prism and spreads into a spectrum. Explain why violet light bends more than red light.
- Violet light has a shorter wavelength and higher frequency compared to red light.
- When light enters a new medium (like glass), its speed changes depending on the wavelength.
- Shorter wavelengths (like violet) slow down more than longer wavelengths (like red), so violet refracts (bends) more strongly
An ocean wave has a speed of 12 m/s. A boat floating on the water bobs up and down 6 times in 15 seconds. Calculate the wavelength
Step 1: Frequency = number of waves ÷ time
= 6 ÷ 15 = 0.4 Hz
Step 2: Wavelength = speed ÷ frequency
= 12 ÷ 0.4 = 30 m
Astronauts on the Moon cannot talk to each other without radios. Explain why in terms of mechanical waves and particle theory.
Sound is a mechanical wave that needs particles (a medium) to vibrate through. The Moon has no atmosphere (no air particles), so sound cannot travel. Radios use electromagnetic waves, which don’t need a medium, allowing communication.