Properties of waves, including light and sound Flashcards
What do waves transfer?
Energy
Waves transfer energy without transferring what?
Matter
Describe wave motion
- No matter travels with waves as it travels between 2 points
- Points on the wave vibrate back and forth about a fixed point
What is a wavefront?
A way of viewing waves from above
What is meant by the speed of a wave?
The distance travelled by a wave per second
What is meant by the frequency of a wave?
Number of waves passing any point per second
What is the SI unit for frequency?
Hertz (Hz)
What is the formula for frequency?
f= 1/period
What is meant by period?
Time taken for 1 oscillation
What is the SI unit for period?
Seconds (s)
What is meant by the term wavelength?
Distance from a point on one wave to the same point on the next wave
What is the SI unit for wavelength?
Metres (m)
What is the formula for speed?
v = fλ
What is meant by the term amplitude?
The height of a wave measured from the middle of the wave
What is a transverse wave?
Waves in which oscillations are perpendicular to direction of travel
What is a longitudinal wave?
Waves in which oscillations are parallel to direction of travel
What are 2 differences between transverse and longitudinal waves?
- Oscillations and direction of travel
2. Transverse waves have peaks and troughs and longitudinal waves have compressions and rarefactions
What are 3 wave effects?
- Reflection
- Refraction
- Diffraction
What is reflection?
The bouncing back of a wave
What is refraction?
The change in speed of a wave when it passes from one medium to another
What is diffraction?
The spreading of a wave
What are the laws of reflection?
- Angle of incidence = angle of reflection
2. The incident ray, reflected ray and the normal all lie in the same plane
What are the effects on speed, frequency and wavelength of a wave that is reflected?
No effect
What are 3 effects of refraction of a wave into a different medium?
- Change in speed
- Change in wavelength
- Change in direction
What is the effect on a wave travelling from a more dense medium to a less dense medium?
- Speed decreases
- Wavelength decreases
- Bends away the normal
What is the effect on a wave travelling from a less dense medium to a more dense medium?
- Speed increases
- Wavelength increases
- Bends towards from the normal
Which property of a wave is not affected by refraction?
Frequency
Is shallow water less dense or more dense than deep water?
Less dense
What are 2 factors that influence diffraction?
- Size of the gap
2. Wavelength
How does the size of a gap affect diffraction?
Wider gaps produce less diffraction
How does wavelength affect diffraction?
Greater wavelength produces more diffraction
What 3 properties are not affected by wavelength?
- Speed
- Wavelength
- Frequency
What are 3 characteristics of an optical image formed by a plane mirror?
- Same size as the object
- Same distance behind the mirror as the object is in front of it
- It is directly in line with the object
Is the image in a plane mirror virtual or real?
Virtual
Exam tip ; )
When drawing light waves being reflected take care to get the angle about right.
If they are slightly out it won’t be a problem, but if there is an obvious difference between the angle of incidence and the angle of reflection then you will probably lose a mark.
Describe an experimental demonstration of the refraction of light
- Place the glass block on plain paper and draw around the block using a pencil
- Use a ray box to project a single ray of light towards the glass block
- Using a pencil, mark the points before it reaches the glass block and where it hits the glass block
- Mark the points where it leaves the glass block and after it has left the glass block
- Connect the points using a ruler and pencil
- Repeat the process with the ray striking the block at different angles
- Use Snell’s Law
What is Snell’s Law?
As light travels from a less dense medium to a more dense medium it slows down and bends towards the normal
What is refractive index?
Degree at which light is bent by the second medium
What is the relationship between angle of incidence and angle of refraction given by Snell’s Law?
n = sin i ÷ sin r