LIGHT Flashcards
(19 cards)
What is dispersion of light
splitting of light
into its different colours
Explain what is meant by refractive index.
ratio of sine of the angle of incidence
// formula
to sine of the angle of refraction
// notation
Explain how the greenhouse effect heats the Earth.
atmosphere / gases
(3)
trap radiation reflected by the Earth
What phenomenon allows light to travel in an optical fibre without escaping?
Total internal reflection
Polaristion
polarisation of wave occurs when the vibrations are confined to one plane only
What is meant by critical angle?
The angle in the denser of two media when the angle in the less dense medium in 90 degrees
Total internal reflection
angle of incidence > critical angle (and all light
Explain the term wavelength
The distance between two crests/troughs
Laws of reflection
1:The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.
2:The angle of incidence is equal to the angle of reflection [I=r]
Reflection
The bouncing of light off an object
Virtual image
an image formed by the apparent intersection of rays
Real Image
An image formed by the actual intersection of light rays
Ray diagram for concave mirror
If the object is outside the focus, the image is real and located in front of the mirror.
If the object is inside or at the focus, the image is virtual and located behind the mirror.
Ray diagram for a convex mirror
The image is always virtual and located behind the mirror.
The image is always diminished. The nearer the object is to the mirror, the bigger the image.
Give one advantage and one disadvantage of using a convex mirror, instead of a plane
mirror, as a wing mirror on a car.
advantage: wide field of view / always erect
disadvantage: image diminished, image distance reduced compared to actual distance
How to get the focal point when given the diameter of an object
Radius divided by two
e.g. diameter=20cm
radius=10cm
10/2=5 therefore focal point =5cm
Why is a convex mirror used as the rear view mirror in a car?
Gives a large field of vision
Image is upright (erect)
Name two uses for a convex mirror
Rear mirror in car / security mirror
Where in the eye is light detected?
Retina
