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(i) O cm – trough and crest interference
(ii) +10 – crest and crest interference
maurice.mutuku answered the question on August 22, 2019 at 12:26
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Sodium has a work function of 2.3eV. Given that: Planck’s constant h = 6.63 x 10-34JS, velocity of light in vacuum, C = 3.0 x108m/s, 1 electron-volt (1eV) = 1.6 x 10-19 C and mass of an electron, me = 9.1 x 10-31kg, calculate:
(i) Its threshold frequency.
(ii) The maximum velocity of the photoelectrons produced when the sodium is illuminated by light of wavelength 5.0 x 10-7m.
(iii) The stopping potential V, with the light of this wavelength.
Date posted: August 22, 2019. Answers (1)
- A G.M tube indicated a constant count rate of 5 counts per minute when a radioactive source was placed at a distance of about 10...(Solved)
A G.M tube indicated a constant count rate of 5 counts per minute when a radioactive source was placed at a distance of about 10 cm from it. When the source was moved close to about 4cm the count rate varied as follows.
(i) The count rate was constant at a distance of 10 cm away. Explain
(ii) Plot a graph of count rate against time.
(iii) Use your graph to estimate the half-life of the radioactive source.
(iv) 
(v) State two precautions that have to be observed when using a radioactive substance.
(vi) Distinguish between fission and fusion.
Date posted: August 22, 2019. Answers (1)
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The figure below shows a circuit.
Calculate:
i) The total resistance of the circuit.
ii) The total current flowing in the circuit.
iii) The voltage drop across resistor R1.
iv) The current through the 3Ω resistor.
Date posted: August 22, 2019. Answers (1)
- The figure below shows a current carrying wire at right angle to a cardboard. Iron fillings are sprinkled on the card and card slightly tapped.(Solved)
The figure below shows a current carrying wire at right angle to a cardboard. Iron fillings are sprinkled on the card and card slightly tapped.
Draw and indicate the direction of the magnetic field pattern displayed on the card.
Date posted: August 22, 2019. Answers (1)
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Explain the behavior of the pins as illustrated below
Date posted: August 22, 2019. Answers (1)
- A house has a lighting circuit operated from a 240V mains supply. Four bulbs rated 40W 240V and six bulbs rated 100W 240V are switched...(Solved)
A house has a lighting circuit operated from a 240V mains supply. Four bulbs rated 40W 240V and six bulbs rated 100W 240V are switched on for 5 hours a day. Determine the monthly bill for the consumer given that the cost of electricity is at shs. 5.50 per unit.
(Take 1 month = 30 days and the standing charge is sh. 150)
Date posted: August 22, 2019. Answers (1)
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A girl standing at a distance claps her hands and hears an echo from a tall building 2 seconds later. If the speed of sound in air is 340m/s, determine how far the building is.
Date posted: August 22, 2019. Answers (1)
- The figure below shows refraction of light at air-water interface.(Solved)
The figure below shows refraction of light at air-water interface.
Determine angle Ө if the refractive index of water is 1.33
Date posted: August 22, 2019. Answers (1)
- Water of mass 3.0kg initially at 200c is heated in an electric kettle rated 3.0kw. The water is heated until it boils at 1000c. (Take...(Solved)
Water of mass 3.0kg initially at 200c is heated in an electric kettle rated 3.0kw. The water is heated until it boils at 1000c. (Take specific heat capacity of water = 4200Jkg-1k-1, Heat capacity of kettle = 450Jk-1, and specific latent heat of vaporization of water = 2.3MJkg-1)
Determine;
(i) The heat absorbed by water.
(ii) The heat absorbed by the electric kettle.
(iii) The time taken by water to boil.
(iv) How much longer will it take to evaporate all the water?
Date posted: August 22, 2019. Answers (1)
- The figure below shows a toy car moving in a circular rail in a vertical plane. The mass of the toy car is 300g and...(Solved)
The figure below shows a toy car moving in a circular rail in a vertical plane. The mass of the toy car is 300g and the radius of the rail is 2m.
Determine:
i) Minimum velocity at which the toy passes point A
ii) If the toy was tied by a string at the centre of the rail path, following the same circular path, when whirled at which position (A or B) would the string experience maximum tension. Explain your answer.
iii) If the toy moves with a velocity of 5m/s as it passes point B, find the angular velocity at this point.
iv) State two applications of uniform circular motion
Date posted: August 22, 2019. Answers (1)
- The diagram in the figure below represents a wheel and axle used as a machine, whose efficiency is 80% to raise 400N of building materials....(Solved)
The diagram in the figure below represents a wheel and axle used as a machine, whose efficiency is 80% to raise 400N of building materials. The wheel and axle have diameters of 75cm and 15cm respectively.
(i) Mark on the diagram the correct position and direction of the load to be lifted.
(ii) Name the principle on which this machine works.
(iii) Calculate the effort needed to raise the load.
(iv) The machine is operated manually and raises the load to a height of 5m in 20 seconds. Calculate the power developed by the operator
Date posted: August 22, 2019. Answers (1)
- A simple hydrometer is set up with a test –tube of mass 10g and length 12cm with a flat base and partially filled with lead...(Solved)
A simple hydrometer is set up with a test –tube of mass 10g and length 12cm with a flat base and partially filled with lead shots. The test – tube has a uniform cross – sectional area of 2.0cm2 and 10cm of its length is under water as shown in the figure below.
(i) Determine the mass of lead shots in the test – tube (Take density of water = 1000kgm-3)
(ii) Calculate the mass of the lead shots to be added if the test – tube has to displace an equal volume of a liquid of density 1.25gcm-3.
(iii) What is the function of the lead shots?
Date posted: August 22, 2019. Answers (1)
- Hooke’s law is written mathematically as F=Ke. Give three factors that letter K depend on.(Solved)
Hooke’s law is written mathematically as F=Ke. Give three factors that letter K depend on.
Date posted: August 22, 2019. Answers (1)
- A light spring that obeys Hooke’s law was attached to a fixed support. When a load of 10N was hung on it, the length of the...(Solved)
A light spring that obeys Hooke’s law was attached to a fixed support. When a load of 10N was hung on it, the length of the spring was 320mm and when a 20N load was hung on it, the length became 400mm. Determine:
(i) The length of the spring when it has no load on it
(ii) The length of the spring when it has a load of 16N.
Date posted: August 22, 2019. Answers (1)
- The figure below shows two graphs for two different springs A and B(Solved)
The figure below shows two graphs for two different springs A and B
F1 and F2 are points at which the springs break.
Determine and explain which of the two springs:
(i) Obeys Hooke’s law
(ii) Is stronger
Date posted: August 22, 2019. Answers (1)
- The diagram below shows a pendulum bob swinging freely to and from.(Solved)
The diagram below shows a pendulum bob swinging freely to and from.
Determine the maximum velocity of the ball at B if the maximum horizontal displacement of the ball is 10cm.
Date posted: August 22, 2019. Answers (1)
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A ball rolls off a platform of height 1.8 m at a horizontal speed of 15m/s. How far off the edge of the platform does it land? (Take g = 10msˉ²)
Date posted: August 22, 2019. Answers (1)
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Explain the difference between the motion of dust particles in Brownian motion and the motion of dust particles due to convectional currents.
Date posted: August 22, 2019. Answers (1)
- The figure I below shows the reading of a vernier calipers used to get the diameter of a cylindrical tin.(Solved)
The figure I below shows the reading of a vernier calipers used to get the diameter of a cylindrical tin.
If the vernier caliper had a negative error of 0.02 cm, what is the actual diameter of the tin?
Date posted: August 22, 2019. Answers (1)
- i)Derive an expression for the heat lost by the steam as it condenses to water at temperature T.
ii)Derive an expression for the heat gain in...(Solved)
Steam of mass 3.0g at 100 degress celsius is passed into water of mass 400g at 10 degrees celsius. the final temperature of the mixture is T. The container absorbs negligible heat. (specific latent heat of vaporization of steam = 2260KJ/kg, specific heat capacity of water =4200J Kg-1 K-)
Date posted: August 13, 2019. Answers (1)