## Physics 2019 Past Question | WAEC Study the following past questions and answers for JAMBWAEC  NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

46. Which of the following statements about a neutral atom is correct? The

• A. core is composed of electrons and protons
• B. number of electrons is equal to that of neutron
• C. number of neutrons is equal to that of protons
• D. number of protons is equal to that of electrons

47. Which of the following properties is not exhibited by sound waves

• A. Diffraction
• B. Polarization
• C. Interference
• D. Reflection

48. When ultraviolet light is incident on certain metallic p articles are emitted. These particles are called

• A. positrons
• B. protons
• C. photoelectrons
• D. photons

49. The graph above illustrates the variation of temperature θwith time (t) for a solid that is being heated. Which processes take place at segments P and Q respectively?

• A. Freezing and vaporization
• B. Evaporation and solidification
• C. Melting and boiling
• D. Condensation and evaporation

### PHYSICS THEORY PAST QUESTIONS 2019 WITH SOLUTION

35.  A ray of light travelling from a rectangular glass block of refractive index 1.5 into air strikes the block at an angle of incidence of 30. Calculate its angle of refraction.

• A. 48.6°
• B. 19.5°
• C. 20.0
• D. 45.0
• (a) (i) Define atomic spectra.
(ii) Differentiate between emission spectra and absorption spectra.

(b)

The diagram above illustrates an electron transition from energy level n = 3 to n = 1. Calculate the:

(i) energy of the photon

(ii) frequency of the photon

(ii) wavelength of the photon [h = 6.6 x 10−34J s, c = 3.0 x 1088 ms−1; 1 ev = 1.6 x 10−19 J]

c)(i)Differentiate between soft x-rays and hard x-rays    (ii) Draw the circuit symbol for a p-n junction diode        (iiii) Give the reason for doping a semiconductor material

2. You are provided with a stopwatch, a meter rule, a split cork, retort stand and clamp, a pendulum bob, a piece of thread, and other necessary apparatus.

1. Place the retort stand on a laboratory stool. Clamp the split cork.
2. Suspend the pendulum bob from the split cork such that the point of support Pof the bob is at height = 100cm above the floor Q. The bob should not touch the floor and should be kept constant throughout the experiment.

iii. Adjust the length of the thread such that the center of the bob is at a height y= AQ= 20cm from the floor.

1. Displace the bob such that it oscillates in a horizontal plane.
2. Take the time t for 20 complete oscillations.
3. Determine the period T of oscillation and evaluate T

vii. Repeat the procedure for four other values of y = 30cm, 40cm, 50cm, and 60cm. In each case, determine and T.

viii. Tabulate the results.

1. Plot a graph of on the vertical axis and y on the horizontal axis, starting both axes from the origin (0,0).
2. Determine the slope, s, of the graph and the intercept c on the vertical axis.
3. If in this experiment SR= c, calculate R.
4. State two precautions taken to ensure accurate results.

(b) i. The bob of a simple pendulum is displaced a small distance from the equilibrium position and then released to perform simple harmonic motion Identify where its:
(∝) kinetic energy is maximum
(β) acceleration is maximum

1. An object of weight 120N vibrates with a period of 4.0s when hung from a spring. Calculate the force per unit length of the spring. [g= 10ms−2, π=3.142]

3. You are provided with a converging lens and holder, a screen, a ray box containing an illuminated object pin, and a meter rule.

• Place the lens in its holder such that it is facing a distant object seen through a well-lit laboratory window. Move the screen to and fro until a sharp image of the distant object is formed on it. Measure the distance, f00, between the screen and the lens.
• Clamp the meter rule securely to the table. Place the illuminated object pin at the end of the meter rule.
• Place the lens at a position such that X = RP =20cm.
• Move the screen to a position to receive a sharp image of the object. Measure the distance Y = PQ.
• Evaluate Z = (X+Y)
• Repeat the procedure for five other values of x = 25cm. 3Ocm, 35cm, 40cm and 45cm. In each case, record X,Y and evaluate Z.
• Tabulate the results.
• Plot a graph with on the vertical axis and on the horizontal axis. Draw a smooth curve through the points.
• Determine from your graph the minimum value of Z=Z00 and its corresponding distance
• Evaluate W = ½ (Z04+X02Z04+X02)
• State two precautions taken to ensure accurate results.
• (b) i. Draw a ray diagram to show how a Convex lens forms an image of magnification less than one.
• Name two pairs of features in the human eye and a lens camera that performs similar functions.

4. You are provided with a battery of e.m.f. E, a key K, a voltmeter, a standard resistor R00= 2Ω, a resistance box R, and some connecting wires.

• Measure and record the e.m.f. of the battery.
• Set up a circuit as shown in the diagram above with the key open.
• Set the resistance on the resistance box to 22.
• Close the key, read and record the potential difference on the voltmeter.
• Evaluate V−1−1
• Repeat the procedures for five other values of R = 5Ω 10Ω,12Ω,15Ω and 20Ω. In each case, record and evaluate V−1
• Tabulate the results.
• Plot a graph with on the vertical axis and V−1 l on the horizontal axis, starting both axes from the origin (0,0).
• Determine the slope, s, of the graph and the intercept c on the vertical axis.
• Calculate ∝and β from the equations s = R0 ∝ and c= – (R00+B).
• State two precautions taken to obtain accurate results.

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