EM Spectrum Flashcards
What is refraction?
When a light wave changes speed and direction when passing through a medium
What is reflection?
When a wave bounces off a surface instead of being absorbed or transmitted
When does total internal reflection occur?
When the incident angle is greater than the critical angle
What is the angle of incidence equal to when total internal reflection occurs?
The angle of reflection
What is diffuse reflection?
When reflected light is scattered in all directions from a non-smooth surface
What is specular reflection?
When light is reflected evenly from a smooth surface
What can white light be split up into?
The colours of the visible spectrum
What do filters of light do?
Absorb every other colour apart from the colour it’s meant to be, it transmits this colour through
Why does refraction occur?
Because light waves travel at different speeds in different materials
What happens to the path of the light when it is refracted in glass?
It bends towards the normal when it enters the glass and bends away from the normal when it leaves the glass
When the incident angle is the same as the critical angle is the light reflected or refracted?
It is the largest the incident angle can be for refraction to happen, reflection only occurs when the incident angle is greater than the critical angle
What determines the colour of an object?
The colour of an object depends on which colours the atoms of the object absorb and which one they reflect
What does a converging lens do?
Bends rays of light towards each other, bringing them to a point, helps with long sightedness
What does a diverging lens do?
Bends rays of light away from each other, helps with short sightedness
What determines the focal length of a lens?
How curved the lens is, the more curved it is the shorter the focal length
What does a shorter focal length mean?
The more powerful the lens is
How do lenses bend light?
Using refraction
Are converging or diverging lenses thicker in the middle?
Converging, diverging are thinner in the middle
What does it mean if an object is ‘at infinity’
The distance between a lens and the object is much greater than the focal length of the lens
What is a real image?
An image that can be produced on a screen, the light rays converge and are focused on the screen
What is a virtual image?
An image formed when the object is between the focal point and the lens
What do light rays appear to do in a virtual image?
Diverge but they don’t actually do this
What is the speed of light?
3x10^8m/s
Do all electromagnetic waves travel at the same or different speeds in a vacuum?
The same
What type of wave are all EM spectrum waves?
Transverse
As the wavelength increases what happens to the frequency of the waves?
It decreases
What is the order of EM waves in terms of energy (lowest to highest)
- Radio waves = Red
- Microwaves = Monkeys
- Infrared = In
- Visible light = Vans
- UV rays = Use
- X-rays = X-ray
- Gamma rays = Glasses
Which type of wave has the highest frequency?
Gamma rays
Which type of wave has the longest wavelength?
Radio waves
What is the typical use of radio waves?
Television signals
What are the typical uses of microwaves?
Cooking and mobile phones
What is the typical use of infrared waves?
Optical fibre communication
What is the typical use of visible light?
Seeing
What are the typical uses of UV rays
Detecting forged bank notes
What is the typical use of x-rays?
Used to make medical images of bones
What is the typical use of gamma rays?
Killing cancer cells
What does the speed of a wave in a material depend on?
The density of the material
How does temperature affect which type of radiation something emits?
The higher the temperature of something is means it will emit radiation with lower wavelengths. The sun produces visible light and UV rays, bodies hotter than the sun emit x-rays
What is intensity?
Power / square metre
What does the temperature of the earth depend on?
The amount of radiation the atmosphere absorbs and how much it emits
What are the dangers of x-rays and gamma rays?
Can cause mutations which can kill cells or result in cancer
What re the dangers of UV rays?
Can damage skin cells and if repeatedly exposed to UV rays can a person can develop cancer
What are the dangers of infrared waves?
Too much infrared radiation can cause skin burns
What are the dangers of microwaves?
They can heat cells which can cause damage to cells or kill them
When is electromagnetic radiation emitted?
When electrons move from a higher to lower energy level
When is electromagnetic radiation absorbed?
When the electrons move from a lower to higher energy level
What happens when energy changes occur in the nucleus of an unstable atom?
High level gamma rays are emitted
What colour in the visible spectrum has the longest wavelength?
Red
