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Phy ws5 to 9 Flashcards | StudBud
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Phy ws5 to 9
Phy ws5 to 9
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1
How are the electrons made into a beam in CRT?
Using a positive anode to focus the electrons
Using a high voltage across the tube
Using an anode to spread the electrons
Using a fluorescent coating at the end of the tube
2
Why is the background radiation from cosmic rays relatively low for most people
Satellites reflect them back into space
Our clothes protect us
We are too far from the Sun
The atmosphere absorbs a lot of cosmic rays
3
After the third half-life, how much of the sample is left?
1/16
1/8
1/3
1/2
4
As a sample of Neon-19 undergoes radioactive decay, its half-life will
Remain constant
Increase
Decrease
Fulctuate
5
..........is the period required for half of a radioactive substance to disintegrate
Half-time
Radioactive
Periodic time
Half-life
6
.......is ionizing radiation present in particular location which is not from deliberate sources.
Thermal radiation
Electromagnetic radiation
D. All of above
Background radiation
7
Electron beam is ……
Colored
Both B and C
Monochrome
Invisible
8
Which more likely description applies to background radiation?
Less natural
Both A and C
More natural
More artificial
9
What steps should be taken if deal with radioactive sources
All of above
Shorten time of exposure from the source
Place shielding behind the source
Increase distance from the source
10
The rays can be seen from the glass of CRT are.........
Electrons
Cathode rays
Both A and B
Light
11
Cathode rays cast ………. Which illustrates they travel in straight lines.
none of above
Beams
scattered shadow
sharp shadow
12
The diagram shows the parts of C.R.O. What is R
Cathode
Accelerating anode
Focusing anode
Control grid
13
Ionizing radiations in living tissues causes.........
the cells to warm up
all molecules to explode
the cells to multiply faster
the molecules in the cells to be broken apart
14
radioactive isotope has a half-life of 2 years. How much of a 400 g sample remains after 6 years
100g
50g
None
200g
15
Find the half-life of isotope from the shown graph.
10 days
15 days
20 days
5 days
16
Ionizing radiation has the ability to knock.........
neutrons out of their shell
electrons out of their shells
protons out of their shell
All of above
17
The number of electrons from grid reaching the screen determines the.........
Picture quality
Brightness level
Sound quality
None of above
18
Who receives the most dose of cosmic radiations
Astronaut
Climbeber
Doctor
Driver
19
…………is the process of emission of electrons from hot metal surfaces.
Thermionic emission
Radioactive emission
Hall effect
D. All of above
20
What happens to the electron when it hits the anode?
stays impeded in the anode
reflects back to the cathode
travels to the voltage source
converts to visible light
21
The waveform display of AC voltage in CRO is...
Birght spot
Average voltage
Peak to peak voltage
Maximum voltage
22
- Which unit is the radiation dose measured in
Sn
Sv
Bq
Rn
23
What can be used to control the direction of cathode rays?
Both A and B
Gravitational field only
Magnetic field only
Electric field only
24
After two half-lives, we still have almost............of the radioactive substance.
75%
0
50%
25%
25
What is the most common source of background radiation
Nuclear waste
Radium
Cosmic rays
Radon
26
The conditions necessary for production of cathode rays are…
low pressure, low voltage
high pressure, low voltage
low pressure, high voltage
high pressure, high voltag
27
What sort of particles make up cathode rays?
Neutron
Proton
All of above
Electron
28
How many electron guns are present in the colored monitors?
4
2
1
3
29
……..are streams of electrons observed in vacuum tubes.
Both A and C
Anode rays
Cathode rays
Cosmic rays
30
What happens to the electron when it is emitted from the cathode
attracted toward the anode
moves around the cathode
goes back to cathode to form equilibrium state
attracted toward the cathode
31
One of the properties of cathode rays are……..
not deflected by electric field
positively charged
moving in straight line in vacuum tube
not deflected by magnetic field
32
Half-life of Zn-71 is 2.4 min. If it is 100 g at the beginning, how many grams would be left after 7.2 min?
8.5 g
25g
15 g
12.5 g
33
Americium-242 has a half-life of 6 h. Starting with 24 g and now have 3 g. How much time has passed?
12h
18h
6 h
24h
34
The colors that are contained in electron guns of TV screen are ……..
Red, orange, green
Black, white, green
Pink, blue, yellow
Red, blue, green
35
Cathode ray tube is used to ......
display pictures on screens
generate positrons
change the state of matter
both A and C
36
The oscilloscope is used to measure...
Time
Frequency
All of above
Voltage
37
How to increase the rate of thermionic emission
increase the surrounding pressure
increase the surface area of the metal
immerse metal in an electrolyte
decrease the temperature of metal
38
The diagram shows the parts of C.R.O. What is Q
Focusing anode
Control grid
Cathode
Accelerating anode
39
……… consists of a specially made cathode-ray tube and different control units of e-beam.
CRO
CPO
CRT
EHT
40
Sweep generator in CRO is used to control...
the brightness of the bright spot
the horizontal deflection of the bright spot
the vertical deflection of the bright spot
the sharpness of the bright spot
41
CRO florescent screen uses the phosphorus isotope......
P-30
P-33
P-32
P-31
42
Why there are aluminum layers on fluorescent screen glass
To accelerate the electron beam
To deflect the electron beam
To produce the visible bright spot
To reduce the chances of phosphor burning
43
Find the half-life of polonium from the shown graph.
3h
5h
4h
2hours
44
What is CRT?
A vacuum tube in which cathode rays are produced
A beam of electrons emitted from a cathode
All of above
A glowing opened glass tube
