(a)(i) Explain the terms: photoelectric emission and threshold frequency; (ii) Einstein’s photoelectric equation can be written as \(E = hf – hf_{o}\) What does each of the symbols used in the equation above represent?
(b) Calculate the frequency of the proton whose energy is required to eject a surface electron with a kinetic energy of \(1.97 \times 10^{-16} eV\) if the work function of the metal is \(1.33 \times 10^{-16}eV\). \((1 eV = 1.6 \times 10^{-18}J; h = 6.60 \times 10^{-34}JS)\).
(c) In a photoelectric cell, no electrons are emitted until the threshold frequency of light is reached. Explain what happens to the energy of the light before emission of electrons begins. State one factor that may affect the numbers of emitted electrons.
(d) Explain what is meant by the duality of matter, illustrating your answer with observation phenomena.
(a) State the laws of electromagnetic induction.
(b) (i) Describe a simple experiment to show how an induced e.m.f, can be produced; (ii) State two factors on which the magnitude of the induced e.m.f. depends
(c) Explain what is meant by the r.m.s. value of an alternating current
(d) (i) If the alternating current is represented by \(I = l_{o} \sin \omega t\), state what the symbol \(I, I_{o}, \omega\) and \(\omega t\)represent.
(ii) Calculate the instantaneous value of such a current, if in a circuit it has r.m.s value of 15.0A when its phase angle is 30Β°.
(a) What is a wave motion?
The equation \(y = A \sin \frac{2\pi}{\lambda} (Vt-X)\) represents a wavetrain in which y is the vertical displacement of a particle at distance X from the origin in the medium through which the wave is travelling. Explain, with the aid of a diagram, what A and \(\lambda\) represent.
(b) (i) Describe an experiment to determine the frequency of a note emitted by a source of sound
(ii) A pipe closed at one end is 1 m long. The air in the pipe is set into vibration and a fundamental note is produced. If the velocity of sound in air is 340ms\(^{-1}\), calculate the frequency of the note
(c) State two differences between a sound wave and a radio wave.
(a) What is meant by the statement: The linear expansivity of a solid is \(1.0 \times 10^{-5}K^{-1}\)?
(b)(i) Describe an experiment to determine the linear expansivity of a steel rod. (ii) Steel bars, each of length 3m at 29Β°C are to be used for constructing a rail line. If the linear expansivity of steel is \(1.0 \times 10^{-5}K^{-1}\), calculate the safety gap that must be left between successive bars if the highest temperature expected is 41Β°C.
(c) State three advantages and two disadvantages of thermal expansion of solids.
The electric force between two point charges each of the magnitude, q at a distance of r apart in air of permittivity is:
- A. q2/4ΟΞ΅r
- B. rΞ΅0/q2
- C. 4Οq/Ξ΅0
- D. qr2/Ξ΅0
- E. \(\frac{q^2}{4\piΞ΅or^2}\)
Calculate the escape velocity for a rocket fired from the earth’s surface at a point where the acceleration due to gravity is 10ms-2 and the radius of the earth is 6 x 106m.
- A. 7.8 x 106ms-12
- B. 1.1 x 104ms-1
- C. 3.5 x 107ms-1
- D. 6.0 x 107 ms-1
- E. 1.2 x 108ms2-1
What is the gravitational potential due to a molecule of mass, m and at a distance, r from it? (G = gravitational constant).
- A. Gm2/r2
- B. Gm/r
- C. Gm2/r
- D. G2m2/r
- E. m2/Gr2
Which of the following is not a property of longitudinal waves?
- A. compression
- B. reflection
- C. refraction
- D. polarization
- E. diffraction
A string is stretched between two points 50cm apart. It is then plucked at its center and the velocity of the wave produced is 300m/s. Calculate the number of vibrations made by the string in 1s.
- A. 3
- B. 6
- C. 150
- D. 300
- E. 600
In a wave the maximum displacement of particles from their equilibrium positions is called.
- A. frequency
- B. amplitude
- C. period
- D. wavelength
- E. wave velocity
A sound pulse sent vertically downwards into the earth is reflected from two different layers of the earth such that echoes are heard 1.2s and 1.4s. Assuming speed of the pulse is 2000ms-1, calculate the distance between the layers.
- A. 200 m
- B. 400 m
- C. 2400 m
- D. 2600 m
- E. 2800 m
Which of the following is a stringed instrument?
- A. flute
- B. trumpet
- C. piano
- D. drum
- E. saxophone
The distance between a node and an anti-node for a transverse wave is equal to
- A. the wavelength
- B. thrice the wavelength
- C. one-half of the wavelength
- D. one-quater of the wavelength
- E. three quaters of the wavelength
The refractive index of a given transparent medium is 1.4. Which of the following is the minimum internal angle for total internal reflection to take place in the medium?
- A. 30o
- B. 36o
- C. 44o
- D. 46o
- E. 54o
The image in a pine-hole camera is always
- A. diminished
- B. enlarged
- C. upright
- D. inverted
- E. blurred
A ray of light is incidence on a plane mirror at an angle of 35o. What is the angle by the reflected ray with the surface of the mirror?
- A. 125o
- B. 70o
- C. 65o
- D. 55o
- E. 35o
A short chain is usual attached to the back of a petrol tanker trailing behind it to ensure that the
- A. petrol tanker is balanced on the wh eel
- B. heat generated by friction in the engine can be conducted to the floor
- C. charges generated by friction in the tanker can be conducted to the earth
- D. the tanker moves slowly as the chain touches the floor
- E. chain produces sound for the resonance of the tanker engine
Which of the following instruments can be used to compare the relative magnitudes of charges on two given bodies?
- A. The electrophorous
- B. Ebonite rod
- C. Proof plane
- D. Gold leaf electroscope
- E. Capacitor
All the heat generated by a current of 2A passing through a resistor of 6Ξ© for 25s is used to evaporate 5 g of a liquid at its boiling point. What is the specific latent heat of the liquid?
- A. 60 Jg-1
- B. 120 Jg-1
- C. 300 Jg-1
- D. 360 Jg-1
- E. 1500 Jg-1
A block of ice at its melting point is left on a table in the atmosphere and observed to melt gradually. Which of the following statements is true about the melting process?
- A. the reaction force of the table on the ice breaks the ice into water molecules
- B. heat extracted from the ice block makes the ice block cold
- C. the ice block absorbs heat from the atmosphere and its temperature rises
- D. the atmosphere absorbs heat from the ice block and its temperature falls
- E. the ice block absorbs heat from the atmosphere and its temperature remains constant as it melts
Calculate the heat energy required to vapourize 50g of water initially at 80oC if the specific heat capacity of water is 4.2Jg-1K (specific latent heat of vapourization of water is 2260Jg-1).
- A. 533000J
- B. 230000J
- C. 117200J
- D. 113000J
- E. 4200J