1994 - WAEC Physics Past Questions and Answers - page 5
41
A light wave travels from air into a medium of refractive index 1.54. If the wavelength of the light in air is \(5.9\times10^{-7}\)m, calculate its wavelength in the medium
A
\(2.5\times10^{-7}\)m
B
\(3.8\times10^{-7}\)m
C
\(4.6\times10^{-7}\)m
D
\(5.2\times10^{-7}\)m
correct option: b
n =\(\frac{wavelength\, in\, air}{wavelength\, in \,medium}= \frac{5.9\times10^{-7}}{1.54}= 3.8\times10^{-7}\)m
Users' Answers & Comments42
The density of a body is \(5\times10^3kgm{^-3}\) and it weighs 1N in air. Calculate the apparent weight of the body when totally immersed in water. (Density of water =\(10^3kgm{-3}, g= 10ms^{-2}
A
0.02N
B
0.08N
C
0.20N
D
0.80N
correct option: d
Upthrust = weight of the water displaced =pvg= 1000 x 2 x \(10^{-5}\)=0.20N \ Apparent weight = weight in air – upthrust = 1-0.2N=0.8N
Users' Answers & Comments43
The density of water is 1g\(cm^3\) while that of ice is 0.9\(cm^3\), calculate the volume change when 90g of ice is completely melted
A
0\(cm^3\)
B
9\(cm^3\)
C
10\(cm^3\)
D
90\(cm^3\)
correct option: c
V = \(\frac{m}{p} \, ice volume= 90 cm^3;water volume =100 cm^3\
Volume change = (100-90) cm^3= 10 cm^3\)
Users' Answers & CommentsVolume change = (100-90) cm^3= 10 cm^3\)