A Health Resource for the Community Science Action Guide

Test Answers

GCSE exercises

Electromagnetic spectrum crossword

e.m. spectrum, match the columns

Radio Waves ==> Terrestrial television
Microwaves ==> Mobile phone transmissions
Infra Red ==> Night vision
Visible Light ==> Optical astronomy
Ultra Violet ==> Forged bank note detection
X Rays ==> Investigating broken bones
Gamma Rays ==> Nuclear medicine

Filling in the gaps

frequency, hearing, detector, echolocation, dolphins, high, electromagnetic, light, soft, bone, CT, MRI, hydrogen, brain.

Imaging Crossword

Ultrasound multichoice

1. Ultrasound uses high frequency sound.
2. For a typical ultrasound scan the frequency of the waves is between 1MHz and 5MHz.
3. Ultrasound works by reflection.
4. An animal that uses ultrasound for echolocation is a dolphin.
5. The speed of sound in tissue is about 1540 m/s.
6. The ultrasound probe uses a crystal.
7. Doppler ultrasound can be used to measure blood flow.
8. Ultrasound can be used to study the heart this is Cardiology.
9. Ultrasound is used for checking a baby's progress because it does not damage cells.
10. Reflections of sound waves are called echoes.

X-rays multichoice

1. X-rays have high frequency.
2. X-rays are transverse waves.
3. X-rays are in the electromagnetic spectrum next to ultra violet waves
4. To make X-rays you need a stream of electrons.
5. The high energy electrons hit a metal anode.
6. X-rays were dicovered in 1895.
7. X-rays are good for imaging bones.
8. X-rays travel at the speed of light.
9. The X in X-rays means X for unknown.
10. X-rays are also used for CT scanning.

A Level solutions

Answer outline and marking scheme for question: 1
(a) (i) 238/92U + 1/0n -> 239/92U
(ii)238/92U -> 239/92Np
[4 marks]
(b) e.g ground acts as good as shield satisfactory for short time but half-lives likely to be long corrosion, leakage etc.
(allow other relevant points)

[4 marks]

Answer outline and marking scheme for question: 2
(a) very hot matter
electrons no longer attached to nucleus [2 marks]

(b) magnetic containment
field in shape of toroid [2 marks]

(c) e.g deuterium is abundant fuel
waste products not radioactive
on system failure, stops automatically
(1 each, max 2) [2 marks]

(d) (i) E = (2.3 x 10exp-28)(2.6 x 10exp-15) = 8.8 x 10-exp14J [1 mark]

(ii) 8.8 x 10exp-14=2 x 1.5 x 1.5 x 1.38 x 10exp-23 x T
T = (8.8 x 10-14) / (2 x1.5 x 1.38 x 10exp-23
= 2.1 x 10 exp9 [2 marks]

(iii) most unlikely that hydrogen will fuse
must be some other reaction [2 marks]

Answer outline and marking scheme for question: 3
(a) particles would collide with gas molecules [1 mark]

(b) arrow tangential
in cavity upwards [2 marks]

(d) e.g radius or orbit
increase in cyclotron
cyclotron has constant magnetic field
whereas it varies in synchrotron
(M1, A1 for each, max. 4)

[4 marks]

Answer outline and marking scheme for question: 4
(a) (i) particle having same mass & opposite charge
e.g . electron/positron
(ii) matter and antimatter combine to give photons only [4 marks]

(b) (i) E insert symbol
(ii) E = hf =1/2 x (1.64 x 10exp-13 / (6.63 x 10exp-34) = 1.24 x 10exp20 Hz
[5 marks]

5. ques.

18 kV accelerating voltage is applied across an X-ray tube. Calculate:
the velocity of the fastest electron striking the target,
the minimum wavelength in the continuous spectrum of X-rays produced.
(Mass of electron = 9 x 10exp-31 kg;
Charge on electron = 1.6 x 10exp-19 C;
h = 6.6 x 10exp-34 Js, c = 3 x 10exp8 m/s)

Solution
--------------------------------------------------------------------------------
V = 18 x 10exp3 V
me = 9 x 10exp-31 kg;
e = 1.6 x 10exp-19 C;
h = 6.6 x 10exp-34 Js,
c = 3 x 10exp8 m/s

v = 8 x 10exp7 m/s
.............................................(i)

min = 0.6875 x 10exp-10, 6.9 x 10exp-11m
.............................................(ii)

Ans: 8 x 10exp7 m/s; 6.9 x 10exp-11 m

6. soln

An X-ray tube is operated with an anode potential of 10 kV and an anode current of 15 mA. Calculate
the number of electrons hitting the anode per second,
the rate of production of heat at the anode stating any assumptions made and
the frequency of the emitted X-ray photon of maximum energy.
e = 1.6 x 10exp-19 C h = 6.6 x 10exp-34 Js

Solution
--------------------------------------------------------------------------------
I = 15 x 10exp-3 A
V = 10 x 10exp3 V
e = 1.6 x 10exp-19 C
h = 6.6 x 10exp-34 Js

= 15 x 10exp-3Cs-1

= 1.6 x 10exp-19C

.............................................(i)

Power = V x I = 10 x 10exp3 x 15 x 10exp-3 = 150 W
Entire range of wavelengths produced gives heat.
.............................................(ii)

hfmax = eV , fmax =

.............................................(iii)

Ans: 9.4 x 10exp16 /s; 150W; 2.4 x 10exp18Hz