# Physics book 3 topic 1 - Radiation

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• Created by: Khalifa
• Created on: 08-03-14 16:20

## 1. The focal length of a lens is 0.5m. Whats the power of that lens?

• 1/0.5 = 2 D
• 0.5/1 = 0.5 D
• 1 x 0.5 = 0.25 D
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## 2. If the angle of incidence (I) is equal to the critical angle...

• Most of the light passes out, a little portion is reflected internally.
• The emerging rays come out along the surface with some left to be internally reflected.
• No light comes out as it all reflects internally (Total Internal Reflection, TIR)
• Nothing happens, it just passes through.

## 3. The energy from a 100W light bulb spreads over a surface of 4m squared. Calculate the intensity of radiation

• 50 W/m squared
• 20 W/m squared
• 25 W/m squared
• 12.5 W/m squared

## 4. Endoscopes use...

• two bundles of optical fibres
• one bundle of optical fibre
• three bundles of optical fibres
• Four bundles of optical fibres

## 5. A Diverging lens will always produce a...

• virtual Image
• real Image