What is a wave?
Waves transfer ENERGY and INFORMATION without transferring MATTER.
What is the definition of a LONGITUDINAL Wave?
Vibrations are PARALLEL to the direction of the wave.
e.g. sound, Secondary Earthquake Waves
What is the definition of a TRANSVERSE Wave?
Vibrations are PERPENDICULAR to the direction of the wave.
e.g. water, rope, electromagnetic waves(light)
How do you measure WAVELENGTH?
The distance between a particular point on a wave and the same point on the next wave.
How do you measure AMPLITUDE?
Amplitude is the maximum displacement of particles from their rest position.
(i,e, the height of the wave from the centre line).
What is meant by the PERIOD of a wave?
The time for one complete cycle of the wave
What is the definition of FREQUENCY?
Frequency is the number of waves per second
What is DIFFRACTION?
Diffraction is the spreading out of waves around an edge or a gap.
When does the most DIFFRACTION occur?
The most diffraction occurs when the gap is the same size as the wavelength.
What type of wave is sound?
- Sound is a LONGITUDINAL wave.
- The source of the sound pushes particles closer together causing regions of high pressure (compression). Then they move further apart resulting in low pressure (rarefaction).
Describe an experiment to measure the speed of sound.
• Start the stop clock when smoke appears as the gun is fired.
• Stop the clock when bang is heard.
• Measure the distance between observer and gun, using a trundle wheel.
• Speed , s = d÷t
(Remember light travels faster than sound)
What is the range of Human Hearing?
20 – 20 000 Hz
Frequencies above 20,000Hz are Ultrasound.
How does changing the AMPLITUDE affect a sound wave?
The larger the AMPLITUDE, the larger the vibration of the source so the LOUDER the sound.
How does changing the FREQUENCY affect a sound wave?
The higher the FREQUENCY the higher the PITCH.
What type of wave is light?
Light is a TRANSVERSE wave which is part of a family of waves called the Electromagnetic Spectrum.
What is the law of reflection?
Angle of incidence = Angle of reflection
What are the properties of an image in a plane mirror?
Properties of image in a plane mirror.
• The image is as far behind the mirror as the object is in front.
• The image is the same size as the object.
• The image is virtual
• The image is laterally inverted.
What is refraction?
- Light slows down and bends towards the normal when it enters optically denser medium.
- Light speeds up and bends away from the normal when it speeds up.
What is a wavefront?
Wavefronts are perpendicular to wave direction.
They are line connecting all the points in reached by a wave or vibration at the same time.
When does total internal reflection occur?
When the angle if incidence is greater than the critical angle.
What happens when the angle of incidence is equal to the critical angle?
The ray emerges along the edge of the block.
What happens when the angle of incidence is less than the critical angle.
The ray is refracted.
What is DISPERSION?
- A spectrum is formed when white light passes through a prism.
- Different colours of light have different frequencies which slow down to different speeds so each colour is refracted by a different angle.
- Violet light is refracted more than red light.
What properties do all electromagnetic waves have in common?
All electromagnetic waves:
• Travel at the same speed in a vacuum (empty space) 300,000,000m/s
• Are transverse waves
