P3

Radiation in Medicane

using radiation to spot illnesses.

X-rays

CAT scans

PET scanners

Endoscopes

Ultrasound

using radiation for treatment.

Radiation therapy

Ultrasound

Lasers

Radiation energy

Radiation

Radiation intensity

I = P ÷ A

Reflection

specular reflection

diffuse reflection

Refraction

refraction doesn't occur when light rays cross into a different medium at 90o.

Total internal reflection

critical angle

The critical angle for most glass is about 42°.

Optical fibres

Light getting in at one end undergoes repeated total internal reflection, even when the fibre is bent, and emerges at the other end.

optical fibres are used in endoscopes that allow surgeons to see inside their patients

Refraction of light by lenses

Converging lenses

The distance from the focus to the middle of the lens is called the focal length.

Diverging lenses

To determine the focus for a diverging lens, you trace the path of the light rays that have left the lens backwards to the point at which they converge. The distance from this point to the middle of the lens is the focal length.

When an object is placed within the focal length of a diverging lens it is magnified and remains the correct way up.

The lens equation

1/focal length (m) = 1/object distance (m) + 1/image distance (m)

This can be rearranged to:

real image

virtual image