1997 - WAEC Physics Past Questions and Answers - page 2
11
When white light is incident on a glass prism the spectrum produced on a screen placed beyond the prism is due to?
A
Diffraction
B
Reflection
C
Refraction
D
Polarisation
correct option: c
Users' Answers & Comments12
At what distance from a simple microscope must an object be placed so that the image 5 times the size of the object is produced 20cm from the lens?
A
2cm
B
3.3cm
C
4cm
D
5cm
correct option: c
M=\(\frac {v}{u}=5\Rightarrow v=5u=20,let u be x\ v=5x if v=20 then 5x=20 therefore x=20/5=4\,u=4cm\)
Users' Answers & Comments13
Whenever light waves are restricted to a specific plane they are said to be
A
Diffracted
B
Refracted
C
Diffused
D
Regularly reflected
correct option: e
Users' Answers & Comments14
A solid material of volume 100\(cm^{-3}\) is heated through a temperature difference of 40°C. Calculate the increase in the volume of the material if its linear expansitivity is 2 x \(10^{-6}K{-1}\)
A
2.4 x\(10^{-2}cm^{-3}\)
B
1.6 x\(10^{-2}cm^{-3}\)
C
8 x\(10^{-2}cm^{-3}\)
D
5 x\(10^{-2}cm^{-3}\)
correct option: a
\(3{\alpha}= \frac{\Delta{V}}{V_1\Delta{T}}\Rightarrow \frac{\Delta{V}}{100\times40}=3\alpha\, where\, \alpha = 2 \times 10^{-6}\ \frac{\Delta{V}}{4000}=6\times10^{-6}\Rightarrow \Delta=4\times10^3\times6\times10^{-6}= 2.4\times10^{-2}cm^{-3}\)
Users' Answers & Comments15
Calculate the quantity of heat released when 100g of steam at 100°C condenses to water(Take the specific latent heat of vaporization of water as 2.3x \(10^6Jkg^{-1}\))
A
2.3x\(10^{1}J\)
B
2.3x\(10^{2}J\)
C
2.3x\(10^{4}J\)
D
2.3x\(10^{5}J\)
16
A fixed mass of gas occupies a volume of 20\(cm^3\) at a fixed pressure of 700mmHg. Assuming that the temperature remains constant, what will be the volume of the gas at 750mmHg?
A
2.5\(cm^3\)
B
15.5\(cm^3\)
C
18.7\(cm^3\)
D
21.4\(cm^3\)
correct option: c
\(v_2=\frac{v_1p_1}{p_2}=\frac{20\times700}{750}=18.66=18.7cm^3\)
Users' Answers & Comments17
A converging lens of focal length 15cm is used to obtain a real image magnified \(1\frac{1}{2}\) times. Calculate the distance of the image from the lens?
A
37.5cm
B
22.5cm
C
15cm
D
7.5cm
correct option: a
If u=x, v = \(1\frac{1}{2}x \Rightarrow if u= 2x,v=3x\
\frac{1}{f}=\frac{1}{u}+\frac{1}{v}; \frac{1}{15}=\frac{1}{2x}+\frac{1}{3x} \times \frac{5}{6}\
X=\frac{75}{76}=12.5, v=3x=12.5\times 3=37.5\)
Users' Answers & Comments\frac{1}{f}=\frac{1}{u}+\frac{1}{v}; \frac{1}{15}=\frac{1}{2x}+\frac{1}{3x} \times \frac{5}{6}\
X=\frac{75}{76}=12.5, v=3x=12.5\times 3=37.5\)
18
A cup containing 100g of pure water at 20°C is placed in a refrigerator. If the refrigerator extracts heat at a rate of 840J per minute, calculate the time taken for the water to freeze. Neglect the heat capacity of the material of the cup. (Specific heat capacity of water =4.2J\(g^{-1}K^{-2}\))((Specific latent heat fusion of water =336J\(g^{-1}\)
A
15minutes
B
20 minutes
C
42 minutes
D
50 minutes
correct option: d
H=pt =mL +mcθ ; 840t= 100x336+100x4.2x20 thus t=420000/840=50minutes
Users' Answers & Comments19
What is the frequency of a radio wave of wavelength 150m if the velocity of radio waves in free space is 3 x \(10^8ms^{-1}\)?
A
4.5 x \(10^{10}\)Hz
B
5x \(10^{9}Hz\)
C
4.5 x \(10^{8}Hz\)
D
2 x \(10^{7}Hz\)
correct option: e
V=f\(\lambda, f =\frac{v}{\lambda}= \frac{3\times10^8}{150}\Rightarrow 2\times10^6\)Hz
Users' Answers & Comments20
Which of the following statements about kinetic theory of matter is not correct?
A
The molecules of matter are always in motion
B
When a body is heated the average kinetic energy of its molecules decreases
C
Molecules of a liquid move more freely than those of a solid
D
Matter is made up of very tiny particles called molecules
correct option: b
Users' Answers & Comments