Waves and the electromagnetic spectrum (topic 4-5) Flashcards
What is a longitudinal wave?
A wave that pass on energy by making particles vibrate. it consists of compressions where particles are pushed together and rarefactions were particles are spread out. e.g sound. The wave motion is parallel to the wave direction.
What the type of wave is the one that consists of crests and troughs.
A transverse wave. don’t require particles. e.g s waves or light. The wave vibrations are perpendicular to the direction of the wave.
What is the frequency of a wave? (Hz)
The number of times it passes a point in one second.
What is a wave period?
The length of time it takes for a wave to pass a point.
What is the amplitude of a wave?
The max distance of a point on a wave away from its rest position.
What is dispersion?
When light separates out into its colours due to their different frequency’s.
How to work out wave speed.
Frequency x wavelength
What is significant about radiowaves?
They are the longest wave with the least amount of energy.
What is significant about gamma rays?
They have the smallest wave with the most amount of energy.
What are the uses of ultra violet?
used in sewage work, disinfecting water and in fluorescent materials.
What are the uses of x-rays?
medical- examining bones, security to detect certain materials and shapes.
What are the uses of gamma rays?
Kills cancerous cells, sterilises equipment and kills bacteria.
What is an interface?
The boundary between two medias (different density’s)
What is the normal?
A line that is perpendicular to the interface.
What happens to a wave as it enters a medium with different density.
Speeds up(less dense): bend away from the normal slows down(more dense): bends towards the normal
What are seismic waves?
s waves and p waves
They are used to see the structure of the earth.
p waves can trave through both solids and liquids.
s waves can only travel through solids.
When does the angle of incidence become the critical angle?
At 90 degrees.
What is the law of reflection?
The angle of reflection is equal to he angle of incidence
what are the hazards of electromagnetic radiation?
- microwaves cause internal heating of body tissues
- infrared radiation is felt as heat and causes skin burns
- X-rays damage cells, causing mutations (which may lead to cancer) and cell death
- gamma rays also damage cells, causing mutations (which may lead to cancer) and cell death.
What is the incident ray?
The incoming ray that hasn’t entered a different medium or been reflected etc.
What is dispersion?
When the light enters a triangle it refracts. When it exits the light disperses into separate colours because of the different frequencies
How do you calculate wavelength?
Wave speed/ frequency
What is the correlation between size of wavelength and amount of energy?
Larger the wavelength, the energy it will contain
What are the uses of ultra violet rays
- disinfects water by killing microorganisms
- used in fluorescent materials
What are the uses of Gamma rays?
- To kill cancerous cells- radiotherapy
- sterilises equipment by killing micro organisms
What can transverse waves travel through
CHECK
Only liquids
What can longitudinal waves travel through?
Liquids and solids
What is the difference between p waves and S waves
Find out
S waves can only travel through solids
P waves can travel through both liquids and solids
How do we hear?
Sounds waves cause the eardrum to vibrate which in turn moves tiny hairs in the cochlea to vibrate and turn into electronic impulses and send to the brain
What is the focal point?
A point at which parallel light rays converts after passing through a converging lens or spread out after a diverging lens
What is a converging lens?
A lens which brings light rays closer together
What do you measure frequency in?
Hertz
Hz
What is refraction?
As light enter a different area of density the light slows down and changes direction. When it exits, it returns to the original direction and spend.
What is dispersion?
When the light enters a triangle it refracts. As it exits the light separates into the different colours because of the different frequencies
As you go up the electromagnetic spectrum, what increases as energy levels decreases
Wavelength
What is total internal reflection?
When light instead of refracting it reflects because the angle of incidence is above the critical angle at 90 ‘ meaning it is totally internally reflected?
How does light travel up optical fibres?
Light enters and is totally internally reflected because the angle of incidence is above the critical angle and is reflected up the tube.
What conditions must there be for total internal reflection to occur?
1) The outer cladding must have a lower density than the core
2) the waves must meet the boundary at an angle greater than the critical angle
What is specular reflection?
Reflection when the waves are reflected of a smooth surface. This means that the reflected light waves will always be parallel.
What is Diffuse reflection?
Reflection when the surface is not smooth and has rough irregularities. The incident wave will then be reflected at many different angles and the reflected rays will not be parallel.
What is a converging lens?
A converging lens bends rays of light towards each other to a single point. E.g. towards your retina in your eye
Converging lens are thick in the middle than the edges.
What is a diverging lens?
A diverging lens bends rays of light out away from each other. It is thinner in the middle than at the edges.
What is the focal length?
The distance from the lens to the focal point (where the lens focus the rays)
What is the definition of a real image?
An image that can be produced on a screen (non electronic). It is formed where light rays converge and actually focused on a screen. A real image is formed by an eye because an image is focused on the retina.
What is a Virtual image?
A virtual image is formed by a converging lens when the object is between the focal length and the lens. It makes the the light rays appear to come but don’t actually come from that image like in a mirror.
S waves can only travel through a material in which state?
In a solid so when produced by an earthquake, a ‘shadow’ is made by the liquid core.
P waves can travel through…
solids and liquids
How do we hear?
1) sound waves cause the eardrum which is a thin membrane to vibrate
2) Tiny bones sat behind the ear drum amplify the vibrations
3) Tiny hairs inside the cochlea are moved by the vibrations and turned into electronic impulses
