Light Flashcards
What is specular reflection?
The reflection of light from a flat surface - all rays of light meeting the surface from one direction reflect in the same direction
What is diffuse reflection?
Light reflects off a rough surface causing all the rays of light to reflect in different directions
How is the light spectrum produced?
Different colours travel at different speeds in glass
Which colour is slowed down least by glass and is refracted least?
Red
Which colour is slow down most by glass and refracted most?
Violet
What colours can the eye only properly detect?
Blue, green and red
How does the eye see other colours?
The eye perceives other colours due to a combination of responses from two or more different types of receptor
What is yellow a combination of?
Red and green
What are the secondary colours?
Magenta, cyan, yellow
What are the primary colours?
Red, blue, green
How is the colour of an opaque object determined?
By the wavelengths of light that are reflected most strongly and all other wavelengths are absorbed
How is the colour of a translucent object determined?
By transmitting wavelengths of light and absorbing others ~ e.g. a red glass bottle transmits red light and absorbs green and blue light
What does a convex lens (converging lens) do?
Focuses light to its focal point
What does a concave lens (diverging lens) do?
Spread light out
What is the principle axis?
Imaginary light that passes straight through the lens that is not refracted
What do all rays parallel to the principal axis do?
Pass through a single point on the principle axis (the focal point)
What is the focal length?
Distance between the centre of lens abs the focal point
How do you measure the focal length?
- Stand near the window
- Hold the lens in one hand and a piece of paper in the other hand
- Make the distance between the lens shorter and longer until the image on the paper in in focus
- Measure the distance between the centre of the lens and the paper - this is the focal length of the lens
How is a convex lens represented?
By a line with two arrows pointing outwards
How do you draw a ray diagram?
- Draw a light ray from the top of the object to the vertical axis running parallel to the principle axis
- From this ray draw a refracted ray running diagonally through the focal point
- Draw a ray from the top of the object running diagonally through the middle of the lens
- Draw a light ray from the top of the object running diagonally through the focal point to the vertical axis
- From this ray draw a refracted ray running parallel with the principle axis
- An image is formed where the three rays meet
What is virtual focus?
Rays of light that are parallel to the principle axis
How are virtual rays represented?
Dotted lines
How are concave lenses represented?
A line with two arrows pointing inwards
What is ultrasound?
A sound with a frequency greater than 20,000 Hz
