Waves ( 1 ) Flashcards
What are waves that pass through a substance?
• Waves that pass through a substance are vibrations which pass through that substances
What are mechanical waves?
• Waves that pass through a substance
What are electromagnetic waves?
• Oscillating electric and magnetic fields that progress through space without the need fro a substance.
How do electromagnetic waves progress through space?
- Without a substance
- Vibrating electric field generates a vibrating magnetic fields which generates a vibrating electric field further away and so on.
What are some examples of electromagnetic waves?
- X Rays
- Gamma Radiation
- Infrared Radiation
- Microwaves
- Light
- Ultraviolet radiation
What are longitudinal waves?
Waves in which the direction of vibration of the particles is parallel to the direction in which the wave travels
What are transverse waves?
Waves in which the direction of vibration is perpendicular to the direction in which the wave travels
What are some examples of seismic waves?
- Electromagnetic waves
* Waves on a string
What does it mean for a wave to be plane polarised?
Vibrations stay in one plane only
What does it mean for waves to be unpolarised?
Vibrations change from one plane to another
What waves can be polarised?
Transverse waves
What waves cannot be polarised?
Longitudinal
What do polarising filters do?
Transmit vibrations in one direction only
What are ordinary light waves?
A mixture of different directions of vibrations
What type of wave are electromagnetic waves?
Transverse
What happens if unpolarised light passes through a Polaroid filter?
- Light will be transmitted on the other side
- Transmitted light is polarised as the filter only allows through light which vibrates in a certain direction, according to the alignment of its molecules
What happens if unpolarised light is passed through two filters?
• Transmitted light intensity changes if one Polaroid is turned relative to the other one
What does it mean by filters being crossed?
- Filters are said to be crossed when the transmitted intensity is a minimum.
- At this position, the polarised light from the first filter cannot pass through the second filter, as the alignment of molecules in the second filter is at 90 degrees to the alignment in the first filters
What is the plane of polarisation of an electromagnetic wave?
Plane in which the electric field oscillates
How do polaroid sunglasses work?
- Reduce the glare of light reflected by water or glass.
* Reflected light is polarised and the intensity is reduced when it passes through the Polaroid sunglasses
How can light be partially polarised?
- Light becomes partially polarised when reflected from some surfaces
- Some of it vibrates in the same direction
