Lenses. Prism and rainbow
Answers are for parents and teachers.
1
A lens has focal length 50 cm. Its optical power in dioptres?
2
2
A lens with D = 2 dioptres: focal length in cm?
50
3
Draw the spectrum colours in order with coloured pencils.
Red → violet.
4
Why is a rainbow seen after rain with the Sun behind us?
Light refracts and reflects in drops and returns to us split into colours.
5
Is a magnifier or glasses lens at home convex or concave? Decide by how it shows text on a page.
If it enlarges — convex; if it shrinks — concave.