The follwing represents the electromagnetic spectrum.
|Gamma Rays| X-rays | Ultraviolet| Visible light| Infra red| Microwaves| Radio waves|
Name the type of electromagnetic radiation that is used to:
1) sterilise surgical instruments. [1mark]
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Gamma Ray.
2) to send a signal to a TV from remote control.[1mark]
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IR
3) Valuable items can be security marked using special ink. The ink can only be seen in ultraviolet radiation.
Explain what happens to make the ink visible. [2]
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當D墨汁被響UV照射時，墨汁分子中的電子會被excited，
當這些電子由興奮狀態跌回ground states時，會release a photon.
As energy levels in the electron shells are quantized,
the wavelength of the photon emitted are also quantized.
E=hf = hc/λ
If the wavelength of the photon falls onto the visible light region,
the ink can be observed by eyes.
4. Explain why skin cells need to be pretected from Ultraviolet radiation.[2]
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Genetic mutation of the skin cells may occur due to exposion under large amount of UV light. Which leads to Skin cancer.
The following information is from an oven that combines a microwave and a grill.
Voltage-230V
Microwave power-0.65kW
Grill power--1.15kW
5. Name 2 types of electromagnetic radiation that the oven can use to cook.[1]
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Microwave,
Infra red.
6. Both are switched on at full power for half an hour. Calculate energy transfered, in kWh, by the oven. [2]
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P=E/t
E=Pt= (0.65+1.15) * 60*60
= 6480kJ
7. Which 2 are the same element? [1]
a) 7proton 7neutron 7 electron
b) 6 6 6
c) 6 8 6
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BC
8. Give your reasons to your answer[1]
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Both contain 6 protons.
9. A Space shuttle takes 9 mins to reach its orbital velocity of 8100m/s
Write down the equation that links acceleration, change in velocity and time taken. [1]
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a=(v-u)t
10. Calculate in m/s, the average acceleration, of the space shuttle during the first 9 minutes of its flight. Show clearly how you work out your answer.
[2]
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a=(v-u)/t
= 8100/(9*60)
=15ms-2
11. How is the velocity of an object diffrerent from the speed of an object? [1]
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speed = distance travelled / time
velocity = displacement / time
12. The space shuttle can stay in orbit around the earth for several weeks. Esplain why it stays in orbit and does not fall. [2]
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The gravitational force provided centripetal force to the space shuttle.
13. As the shuttle returns to earth, friction causes its outside temperature to go as high as 1200C. Why is the underneath of the shuttle covered with black tiles?[1]
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To protect the metal components of the space shuttle from melting.
14. Jill weighs 700N and Greg weighs 500N. They are carried by a charlift to 200m high. Write down the equation that links distance moved, force applied and work done. [1]
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W=Fs
15. Calculate work done to lift Greg and Jill. [3]
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Jill:
W=700 x 200 = 140kJ
Greg:
W=500 x 200 = 100kJ
16. The chair takes 5mins to move from the bottom to the top of the ski slope. Use the following equation to calculate the power required to lift Greg and Jill to the top of the ski slope. [2]
power=work done/ time taken
Power=(140000+100000)/(5 x 60)
=800Watt
17. What word can be used for "the flow of electrons"? [1]
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electricity.
18. How is a thermistor affected by an increase in temperature? [2]
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When the temperature increase, the resistance of the thermistor decrease.
19. Write down the equation that links acceleration, force and mass. [1]
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F=ma
20. Write down the equation that links current, potential difference and power. [1]
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P=IV
21. Use the theory of plate techtonics to explain sea floor spreading. [2]
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I dunno what the hell is it lol
22. What evidence is there to support the idea of sea-floor spreading?[1]
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唔知係乜 XD
23. Write down the equation that links frequency, wavelength and wave speed. [1]
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c=fλ
24. A lens is used as a magnifying glass. What type of lens is it? [1]
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Convex lens.
25. Two points are marked as F. In ray diagrams. What are these points? [1]
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Focus
26. What is the name of the straight line which goes through F, through the centre of the lens, and through F on the other side? [1]
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Principal axis.
27. Write down the equation, in words, which you need to use to calculate momentum. [1]
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p=mv
28. Write down the equation which connects change in momentum, force and time. [1]
<<<
F=p/t
29. Which part of an atom emits a beta particle? [1]
<<<
A neutron in the nucleus.
30. How does the composition of an atom change when it emits a beta particle? [1]
<<<
No of proton +1
No of neutron -1
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發表於 3/3/2005 10:42 PM 
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