concave and convex lenses

Describe the structure / symbol of a convex lense

Thicker at the centre than edges

Arrow looking symbol

What do all lenses do

Refract light

How do you draw a raw diagram for a convex lense

-draw out principle axis (straight/ dotted line across paper)

-draw in your object and convex lense symbol with focal length on each side

• draw a line from top of image through the centre of the lens

• Draw straight line from top of image to lens

• And then connect it down to focal length and draw down till it meets other ray of light

Then add in image using arrow and identify change

from looking at a ray diagram how can you identify if an image is real or virtual

The image is real if the light rays meet at a point

identify properties of image from diagram

Larger/ magnified

Inverted

Real

What does convex lens do

Focuses parallel rays of light to a point which is called the principle focus

What is the distance from lens to principle focus

The focal length

Describe the structure and symbol of concave lens

Thicker at edges than centre

What does the concave lense do

Make light rays spread out , the light rays diverge

If you plot lines behind the lens they come to a point (principle focus)

A concave lens doesn’t actually focus light at principle focus , light rays only appear to be coming from principle focus

What will a concave lens image always be

diminished

The right way up

Virtual

How to draw ray diagram for a concave lens

• draw the principal axis

• Draw the object , concave lens symbol and focal point

• Draw light ray going from the top of the object to the centre of lens and down

• Draw a line from object to lens

• Draw dotted line from focal point to lens and make solid line

• Add your image arrow and identify change