What is the frequency of a wave?
The number of waves that pass a point per second
What is the amplitude of a wave?
The height of a wave from rest to crest
What is the period of a wave?
The time it takes for one complete wave to pass a point
What is the wavefront of a wave?
An imaginary surface that represents corresponding points on waves vibrating in unison.
What is the Doppler effect
The Doppler effect is when there is a change in the observed frequency and wavelength of a wave when the source is moving relative to an observer.
Explain the Doppler effect
For example:
1. When a source is moving away from an observer, the waves it emits bunch up in front of it and spread out behind it.
2. This causes the observer to observe an increase in wavelength and decrease in frequency of the waves emitted from the source.
List the order of the electromagnetic spectrum in terms of increasing frequency and decreasing wavelength
- radio waves
- microwaves
- infrared waves
- visible light
- ultraviolet light
- X-rays
- gamma rays
Name the colours of the visible light spectrum in terms of increasing frequency
- red
- orange
- yellow
- green
- blue
- violet
what are the uses of radio waves?
broadcasting and communications
what are the uses of microwaves?
cooking and satellite transmissions
what are the uses of infrared?
heaters and night vision equipment
what are the uses of visible light?
optical fibres and photography
what are the uses of ultraviolet?
fluorescent lamps
what is the use of X-rays?
Observing the internal structure of objects and materials, including for medical procedures
what are the uses of gamma rays?
sterilising food and medical equipment
What is the danger of microwaves?
- internal heating of body tissue
- microwave ovens have shielding to prevent microwaves from reaching the user
What is the danger of infrared?
- skin burns
- wear protective clothing such as oven gloves
What are the dangers of ultraviolet?
- damage to surface cells and blindness
- wear sunscreen with UV filters and stay out of strong sunlight
What are the dangers of gamma rays
- cancer and mutation
- radioactive sources of gamma rays should be kept in lead-lined boxes
What is the critical angle?
The incident angle that gives total internal reflection when exceeded.
How is total internal reflection used in optical fibres?
The core of the fibre is so narrow that light passing through it always hits the core-cladding boundary at angles greater than the critical angle, so is always totally internally reflected.
How is total internal reflection used in prisms?
- Prisms are used in a periscope to see things that aren’t in our line of sight.
- The ray of light travels into one prism at an angle greater than C so it is totally internally reflected at 90 degrees.
- It then travels into another prism below and is totally internally reflected at 90 degrees again.
- The ray is now travelling parallel to its initial path but at a lower height.
