3a.2 - Refractive Index and Ray Diagrams Flashcards
What is refraction caused by?
Waves changing speed
What way does light bend when it enters a denser medium?
It slows down and bends towards the normal
What happens when light hits a boundary at 90 degrees?
It doesn’t change direction but it slows down
What is refractive index?
It is the ratio of speed of light in a vacuum to speed of light in that medium
What is another name for a converging lens?
Convex
What is another name for a Convex lens?
Converging
What is another name for a diverging lens?
Concave
What is another name for a concave lens?
Diverging
What is a virtual image?
It cannot be projected on to a screen
Where do the rays of light go on a converging lens ray diagram? (2)
- One through the top and through the focal point with an arrow
- One through the centre with an arrow
Where do the rays of light go on a diverging lens ray diagram? (4)
- One from the top of the object, stopping at the centre
- A dotted line from the first focal point to the line then draw the line on
- Draw a line straight through
- Arrows
What type of ray diagram always shows a virtual image?
Diverging
What type of lenses do magnifying glasses use?
Converging
State the magnification formula
Magnification = image height % object height
What is the equation for calculating the power of a lens?
Power = 1
————-
Focal length
What is the unit for power of a lens?
Dioptres (D)
What is the focal length of a lens determined by? (2)
- The refractive index
- The curvature of the two surfaces of the lens
What are the three pairs of words that describe an image?
Magnified or diminished Upright or inverted
Real or virtual
Which lens has a negative power?
Diverging
