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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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.

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

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

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.

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 2013PP2QN10

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

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

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FORM I - PHYSICS SYLLABUS

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FORM III - PHYSICS SYLLABUS

FORM IV - PHYSICS SYLLABUS

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