P5 EM Spectrum Flashcards
What is the correct order of wavelengths
Radio, micro, infra-red, visible, ultra violet, X-ray, gamma
Order of colours from low energy to high
Red, orange, yellow, green, blue, indigo, violet
Total internal reflection
Happens when a wave is travelling from a more dense to a less dense material, if the angle of incident is greater than the critical angle for that material it will be fully reflected back into the material, not refracted through
Specular reflection
When a wave reflects of a smooth surface and all of it reflects ht same so an image can be seen from the reflection, done by a mirror
Diffuse reflection
When a wave reflects off a ruff surface and lots of waves are reflected in different directions
A red shirt appears red because
It reflects the red wavelengths of light and absorbs the other wavelengths of visible light
A red filter makes light red because
The red wavelengths of light will transmit through but the other wavelengths will be absorbed
Converging lens
Convex, focuses light in front of the lens, a powerful lens is thicker and has a shorter focal legnth
Diverging lens
Concave, focuses the light behind the lens creating a virtual image, not a real one. More powerful lenses are thicker and spread out the light more
How do you create virtual images with lenses
Diverging lenses always focus the light behind the lens and so always create virtual images, converging lenses will only focus behind the lens if the object is closer than the focus of the lens
How to create real images with lenses
Only converging lenses will focus the image in front of the lens, if the object is further than the focus of the lens
Uses of radio waves
Broadcasting, communications and satellite transmissions
Uses of micro waves
Cooking, communication(satellite transmission), mobile phones
Uses of infra-red
Short range communication, e.g. TV remotes, cooking, thermal imaging, security systems(IR trip wires), fibre optics
Uses of visible light
Visio, photography, illumination
Uses of UV
Fluorescent lighting, sterilising food and medical equipment, used by the body to help create vitamin D, security markings, detecting forged bank nootes
Uses of X-rays
Medical imaging, radiotherapy, airport security scanners
Uses of gamma rays
Medical imaging(CT scans), sterilising food/ medical equipment, radiotherapy
Dangers of radio waves
They are harmless
Dangers of micro waves
Boils water, so can be dangerous and harm internal organs
Dangers of infra-red waves
Burns
Dangers of visible light
High quantities can damage the retina
Dangers of UV waves
Can cause skin cancer
Dangers of X-rays
Can cause cancer
Danger of gamma waves
Can cause cancer
Formula to work out the power of a lens
P=1/f P=optical power in diopters, f = focal legnth
How are radio waves created
Electrons in a circuit are made to oscillate (move back and forward in a closed circuit), the vibrations from which emits radio waves
How are radio waves picked up
Radio waves cause electrons in circuits on the detectors to oscillates, these oscillations are pick up
What do powerful lenses look like?
thicker so can refract light more
