P14 - Light Flashcards
What is reflection
When a wave hits a boundary/surface and instead of travelling to the new medium, it bounces back
What is the normal line
The line perpendicular to the surface/ boundary (plane)
Angle of incidence = _______?
Law of Reflection
Angle of incidence = angle of reflection
The incidence and reflected rays also have the same frequency, speed and wavelength
What is specular reflection
Reflection from a smooth surface where all of the reflected light rays go in one direction
Specular reflection produces an image
What is diffuse reflection
Reflection from a rough surface where the reflected light rays are scattered in different directions
Diffuse reflection doesn’t produce an image
What is a virtual image
The image from which light rays appear to be coming from
Describe the image formed by a plane mirror
Virtual, upright and laterally inverted
Defenition of Refraction
The change in direction of a light ray as it passes the boundary between two different transparent substances
How do colour filters work?
They absorb certain colours and transmit others e.g. white light on a red filter only transmits red light
Primary colous of light
Red, green, blue
Secondary colours of light
Cyan, Yellow, Magenta
What colour would a red object look like through a blue filter
Black as all colours would be absorbed
Why does an object have a certain colour e.g. a red apple
The apple absorbs all other colours and only reflects the red
Defenition of transparent object
An object that transmits all the light that enters it
Defenition of a translucent object
An object that tramsits all the light, but it is refracted in the process
Defenition of an opaque object
An object that doesn’t trasmit any light. All the light is either scattered, reflected or absorbed
What is a convex lens and what do they do
- A lens that is thicker at the centre than it is at the edges
- It is shown by a line with outwards facing arrows
- They converge parallel light rays to a principal focus point and the distance from the centre of the lens to the focal point is the focal length
- The centre light ray doesn’t get refracted as it is passing along the normal (the principal axis
What is a concave lens and what do they do
- A lens that is thicker at the edges than at the centre
- It is shown by a line with inwards facing arrows
- They diverge parallel light rays so the principal focus is behind the lens where the light rays came from - the light rays only appear to be coming from this point
Will the image formed by a convex lens be real or virtual
It can be either
Will the image formed by a concave lens be real or virtual
Always virtual
Describe the image formed by a concave lens
It will always be virtual, upright and diminished
Describe the image formed by a convex lens when the object is more than 2 focal lengths away from the lens
Real, inverted and diminished
Describe the image formed by a convex lens when the object is between 1 and 2 focal lengths away from the lens
Real, inverted and enlarged
Describe the image formed by a convex lens when the object is inside its focal point
Virtual, upright and enlarged
Colours in the light spectrum
- Red, orange, yellow, green, blue, indigo and violet
- On the left is red which has a lower frequency and longer wavelength and on the right is violet which has a higher freqeuncy and a shorter wavelength
Equation for magnification
magnification = image height/object height
magnfication doensn’t have units as it is a ratio
