WAEC Physics Past Questions & Answers - Page 230

1,146.

Whenever light waves are restricted to a specific plane they are said to be

A.

Diffracted

B.

Refracted

C.

Diffused

D.

Regularly reflected

E.

Plane polarized

Correct answer is E

No explanation has been provided for this answer.

1,147.

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

E.

15cm

Correct answer is C

M=\(\frac {v}{u}=5\Rightarrow v=5u=20,let u be x\\ v=5x if v=20 then 5x=20 therefore x=20/5=4\,u=4cm\)

1,148.

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

E.

Interference

Correct answer is C

No explanation has been provided for this answer.

1,149.

Which of the following explains why a thick glass cup cracks when boiling water is poured into it?

A.

Unequal expansion of the exterior and interior walls of the cup

B.

Anomalous expansion of the water

C.

Greater specific latent capacity of water compared with that of glass

D.

Large increase in the heat capacity of the cup

E.

High density of the water

Correct answer is A

No explanation has been provided for this answer.

1,150.

Steel bars each of length 3m at 28°C are to be used for constructing a rail line. If the linear expansitivity of the steel is 1 x \(10^{-5}K^{-1}\),what is the safety gap that must be left between the successive bars if the highest temperature expected is 40°C?

A.

1.2x \(10^{-1}cm\)

B.

7.2x\(10^{-1}cm\)

C.

6x\(10^{-1}cm\)

D.

3.6x\(10^{-2}cm\)

E.

1.8x\(10^{-1}cm\)

Correct answer is D

\(\alpha= \frac{\Delta{L}}{L_1\Delta\theta}; \Delta{L}=\alpha{L_1}\Delta\theta\Rightarrow 1.0\times 10^{-5}\times 300\times (40-28)= 0.036 or 3.6\times 10^{-2}\)