STP Waves & Rad 122 cards

Tagged as: travel, nursing, earth, geography, physics, economics, astronomy

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1

For the types of radiation, give the symbol, what stops them and the range they travel in air.

Alpha (α), absorbed by paper, range about 10cm. Beta (β), absorbed by up to 1cm Al, or 2-3mm of Pb, range about 1m. Gamma (γ) absorbed by thick lead (several cm) or thick concrete (more than 1m), unlimited range.


3

How are the different types of radiation affected by electrical fields?

Alpha is positive so it is attracted to the negative electrode. Beta is negative so it is attracted to the positive electrode. Gamma is not affected.

4

Which type of radiation are deflected by magnetic fields?

Alpha and beta, (gamma is not affected).

5

Which radioactive source is best used as a tracer in the body?

Gamma, with a very short half life. It can easily escape to be detected outside the body.

6

When rolling thin sheets (e.g. paper, rubber), which radioactive source is the best to use to control the thickness?

Beta. Less beta detected = too thick, more = too thin. (alpha would not pass through and gamma would not change)

7

Which radioctive source is most dangerous when inside the body?

Alpha. It is the most ionising and is easily absorbed. Beta and gamma are less likely to be absorbed.

8

Which radioactive source is the least dangerous when outside the body?

Alpha. It can not penetrate the body unlike beta and gamma.

9

What is half-life?

The time taken for the number of nuclei in an isotope to halve.

10

If there are 1000 unsatble nuclei in a substance with a half-life of 10 days, how many will be left after 30 days?

30 days = 3 x half-life. 1000 to 500 (1st half-life), 500 to 250 (2nd half-life), 250 to 125 (3rd half-life). So there will be 125 left.

11

What can damage to cells, in organs, due to radiation cause?

Cancer, the larger the dose of radiation, the greater the risk of cancer.

12

Why can we see stars?

They give out light.

13

What can telescopes detect when studying space?

Visible light or other EM radiation like radio waves or X-rays.

14

What is the difference between a reflecting and a refracting telescope?

Reflecting uses mirrors and refracting uses lenses to produce sharper more detailed images. Both can only be used at night.

15

Describe a radio telescope, used to detect long radio waves from space.

Most have a parabolic dish to reflect the long radio waves to a receiver which can amplify the signal.

16

Where is the best place to have a telescope to study space?

In space as this stops atmospheric interference (clouds, poor weather, light pollution etc). If on Earth, they are put on top of mountains in remote areas with low level pollution.


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20

What is the Big Bang theory?

The universe is expanding after exploding suddenly from a very small point. Space, time and matter were created in the big bang.

21

What discovery supports this theory?

Red-shift and background microwave radiation discovered in 1965.

22

The further away the galaxy the greater the what?

Red-shift observed from Earth.