Free KCSE Physics Topical Questions KNEC Standards

State how the intensity of X-rays in an X-ray tube can be increased.

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN10

State how the intensity of X-rays in an X-ray tube can be increased.

answer

By increasing the heating current in order to produce more electrons

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K.C.S.E Physics Q & A - MODEL 2016PP2QN10

27/7/2020

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K.C.S.E Physics Q & A - MODEL 2016PP2QN10

Figure 6 shows a narrow beam of X-rays passing between two metal plates in air. The plates are connected in series with a switch, a cell and a milliameter.

It is observed that when the switch is closed a current flows in the milliameter. Explain this observation.

answer

X-rays cause ionization of air molecules between the plates. The ions move to plates of opposite charge.

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The anode of an x-ray tube becomes hot when the tube is in use. State the reason for this.

23/7/2020

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K.C.S.E Physics Q & A - MODEL 2014PP2QN11

The anode of an x-ray tube becomes hot when the tube is in use. State the reason for this.

answer

It stops the fast moving electrons V whose kinetic energy is converted to heat.

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K.C.S.E Physics Q & A - MODEL 2013PP2QN10

23/7/2020

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K.C.S.E Physics Q & A - MODEL 2013PP2QN10

Figure 5 shows a narrow beam of x-rays passing between two metal plates in air. The plates are connected in series with a switch, a cell and a milliameter.

It is observed that when the switch is closed a current flows in the milliameter. Explain this observation.

answer

X rays ionise air molecules between plates
Ions move to plates of opposite sign

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K.C.S.E Physics Q & A - MODEL 2012PP2QN018

21/7/2020

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K.C.S.E Physics Q & A - MODEL 2012PP2QN018

 Figure 18 shows parts of an x-ray tube.

(a) Explain why:
(i) A potential difference is applied to the filament.
(ii) A high potential difference is applied between the cathode and the anode.
(iii) Most of the tube is surrounded by lead.
(b) State how the resulting x-rays are affected by increasing the potential difference between the anode and the cathode.
(c) Light of frequency 7.5 x 10¹⁴ Hz strikes a metal surface whose work function is 4.0 x 10^-19J. Determine the kinetic energy of the emitted photoelectrons. (take planks constant h = 6.63 x 10^-34 Js)

answers

(a) (i) To produce electrons; by thermionic emission;
(ii) To accelerate the electrons to give them enough K.E. t produce X-rays at the anode;
(iii) To absorb stray X-rays, thus protecting the operator from those rays;
(b) Increases K.E. of electrons and hence causes X-rays of higher frequency;
OR
X - ray are more penetrative
X - rays of shorter wavelength.

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An x-ray tube produces soft x-rays. State the adjustment that may be made so that the tube produce s hard x-rays.

19/7/2020

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K.C.S.E Physics Q & A - MODEL 2010PP2QN12

An x-ray tube produces soft x-rays. State the adjustment that may be made so that the tube produce s hard x-rays.

answer

Increase the acceleration voltage by setting a higher value.

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K.C.S.E Physics Q & A - MODEL 2009PP2QN11

17/7/2020

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K.C.S.E Physics Q & A - MODEL 2009PP2QN11

In an X- ray tube it is observed that the intensity of X- rays increases when potential differences across the filament is increased. Explain this observation

answer

Increases in P d increases 1 in filament OR. Increase in P d increases heating effect this produces more electrons by Thermionic Emission.
Hence results on more intense x - rays

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K.C.S.E Physics Q & A - MODEL 2008PP2QN19

16/7/2020

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K.C.S.E Physics Q & A - MODEL 2008PP2QN19

(a) X- rays are used for detecting cracks inside metal beams
(i) State the type of the X- rays used
(ii) Give a reason for your answer in (i) above
(b) Figure 13 shows the features of an X- ray tube

(i) Name the parts labeled A and B
A
B
(ii) Explain how a change in the potential across PQ changes the intensity of the X- rays produced in the tube.
(iii) During the operation of the tube, the target becomes very hot. Explain how this heat is caused
(iv) What property of lead makes it suitable for use as shielding material?
(c) In a certain X- ray tube, the electrons are accelerated by a Pd of 12000V. Assuming all the energy goes to produce X- rays, determine the frequency of the X- rays produced. (Plank's constant h= 6.62 x 10,^-34 Js and charge on an electron, e = 1.6 x 10^-19C).

answers

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The accelerating potential of a certain X-ray tube is increased. State the change observed on the X-rays produced.

16/7/2020

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K.C.S.E Physics Q & A - MODEL 2008PP2QN13

The accelerating potential of a certain X-ray tube is increased. State the change observed on the X-rays produced.

ANSWER

Frequency increases
Becomes hard
Wavelength decreases
Strength / quality

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State with a reason the effect on the X- rays produced in a n X- ray tube, when the p.d across the tube is increased

14/7/2020

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K.C.S.E Physics Q & A - MODEL 2006PP2QN14

State with a reason the effect on the X- rays produced in a n X- ray tube, when the p.d across the tube is increased

ANSWER

Resulting X- rays have shorter wave length/ hard/ high frequency because electrons have higher K.E

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The target of X-ray tube s made of melting point. Give a reason for this

13/7/2020

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K.C.S.E Physics Q & A - MODEL 2005PP1QN33

The target of X-ray tube s made of melting point. Give a reason for this

ANSWER

To withstand the high temperature (immerse heat) prevent the target from melting due to high temperature or immense heat.

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State the difference between hard X-ray and soft X-rays.

12/7/2020

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K.C.S.E Physics Q & A - MODEL 2004PP1QN33

State the difference between hard X-ray and soft X-rays.

answer

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State the difference between X-rays and Gamma rays in the way in which they are produced.

12/7/2020

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K.C.S.E Physics Q & A - MODEL 2004PP1QN28

State the difference between X-rays and Gamma rays in the way in which they are produced.

answers

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State the property of X-rays, which makes it possible to detect cracks in bones.

10/7/2020

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K.C.S.E Physics Q & A - MODEL 2002PP1QN32

State the property of X-rays, which makes it possible to detect cracks in bones.

answer

Penetrating power

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State the factor that determines the hardness of the X – rays produced in an X – ray tube.

9/7/2020

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K.C.S.E Physics Q & A - MODEL 2001PP1QN33

State the factor that determines the hardness of the X – rays produced in an X – ray tube.

answers

Pd across Anode – cathode Or anode potential (voltage)

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State and explain the effect of increasing the E.H.T in an x-ray tube on the X-rays produced.

8/7/2020

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K.C.S.E Physics Q & A - MODEL 2000PP1QN35

State and explain the effect of increasing the E.H.T in an x-ray tube on the X-rays produced.

answers

X – rays produces
- Hard X – rays are produced

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State the energy transformation when fast moving electrons are suddenly stopped by a target in an X- ray tube.

7/7/2020

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K.C.S.E Physics Q & A - MODEL 1999PP1QN23

State the energy transformation when fast moving electrons are suddenly stopped by a target in an X- ray tube.

ANSWER

Kinetic energy ray / heat energy.

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State one industrial use of X – rays

6/7/2020

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K.C.S.E Physics Q & A - MODEL 1998PP1QN04

State one industrial use of X – rays

ANSWER

Detecting imperfection in metal structures/block/flaw

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FORM I - PHYSICS SYLLABUS

Introduction to Physics (4 Lessons)
Measurements 1 (12 Lessons)
Force (16 Lessons)
Pressure (24 Lessons)
Particulate Nature of Matter (12 Lessons)
Thermal Expansion (12 Lessons)
Heat Transfer
Rectilinear Propagation of Light and Reflection at Plane Surface (16 Lessons)
Electrostatics (12 Lessons)
Cells and Simple Circuits (12 Lessons)

FORM II - PHYSICS SYLLABUS

Magnetism (12 Lessons)
Measurements II (16 Lessons)
Turning Effect of Force (10 Lessons)
Equilibrium Centre of Gravity (12 Lessons)
Reflection at Curved Surfaces (16 Lessons)
Magnetic Effect of Electric Current (18 Lessons)
Hooke's Law (8 Lessons)
Waves (14 Lessons)
Sound (12 Lessons)
Fluid Flow (14 Lessons)

FORM III - PHYSICS SYLLABUS

Linear Motion (20 Lessons)
Refraction of Light (20 Lessons)
Laws of Motion (15 Lessons)
Energy, Power and Machines (20 Lessons)
Current Electricity (20 Lessons)
Waves II(10 Lessons)
Electrostatics II (15 Lessons)
Heating Effect of Electric Current (10 Lessons)
Quantity of Heat (20 Lessons)
Gas Laws (15 Lessons)

FORM IV - PHYSICS SYLLABUS

Thin Lenses (20 Lessons)
Uniform Circular Motion (10 Lessons)
Floating and Sinking (15 Lessons)
Electromagnetic Spectrum (15 Lessons)
Electromagnetic Induction (20 Lessons)
Mains Electricity (10 Lessons)
Cathode Rays and Cathode Ray Tube (10 Lessons)
X-rays (8 Lessons)
Photoelectric Effect (15 Lessons)
Radioactivity (15 Lessons)
Electronics (10 Lessons)

State how the intensity of X-rays in an X-ray tube can be increased.

K.C.S.E Physics Q & A - MODEL 2016PP2QN10

The anode of an x-ray tube becomes hot when the tube is in use. State the reason for this.

K.C.S.E Physics Q & A - MODEL 2013PP2QN10

K.C.S.E Physics Q & A - MODEL 2012PP2QN018

An x-ray tube produces soft x-rays. State the adjustment that may be made so that the tube produce s hard x-rays.

K.C.S.E Physics Q & A - MODEL 2009PP2QN11

K.C.S.E Physics Q & A - MODEL 2008PP2QN19

The accelerating potential of a certain X-ray tube is increased. State the change observed on the X-rays produced.

State with a reason the effect on the X- rays produced in a n X- ray tube, when the p.d across the tube is increased

The target of X-ray tube s made of melting point. Give a reason for this

State the difference between hard X-ray and soft X-rays.

State the difference between X-rays and Gamma rays in the way in which they are produced.

State the property of X-rays, which makes it possible to detect cracks in bones.

State the factor that determines the hardness of the X – rays produced in an X – ray tube.

State and explain the effect of increasing the E.H.T in an x-ray tube on the X-rays produced.

State the energy transformation when fast moving electrons are suddenly stopped by a target in an X- ray tube.

State one industrial use of X – rays

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FORM I - PHYSICS SYLLABUS

FORM II - PHYSICS SYLLABUS

FORM III - PHYSICS SYLLABUS

FORM IV - PHYSICS SYLLABUS

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