JAMB Physics Past Questions & Answers

1,011.

The absolute refractive indices of glass and water are $\frac{3}{2}$ and $\frac{4}{3}$ respectively. The refractive index at the interface when a ray travels from water to glass is

$\frac{1}{2}$

$\frac{8}{9}$

$\frac{9}{8}$

$\frac{17}{12}$

View answer & explanation

Correct answer is C

Ray travelling from water to glass;

$\frac{\text{speed of light in air}}{\text{speed of light in glass}}$ = $\frac{3}{2}$

= 3 x 108ms-1

X = 2 x 108ms-1

$\frac{\text{speed of light in air}}{\text{speed of light in water}}$ = $\frac{4}{3}$

= $\frac{3 \times 10^8}{g}$

Y = 2.25 x 108ms-1

from water to glass;

Refractive = $\frac{\text{speed of light in water}}{\text{speed of light in glass}}$

= $\frac{2.25 \times 10^8}{2.00 \times 10^8}$

= 1.125

= $\frac{9}{8}$

1,012.

The driver in a motor car, of which the total mass is 800kg and which is traveling at 20ms^-1, suddenly observes a stationary dog in his path 50m ahead. If the car brakes can exert a force of 2000N, what will most likely happen?

the car will be able to stop immediately the driver notices the dog

the car will stop 30m after hitting the dog

the car will stop 20m in front of the dog

the driver will quickly reverse the car

the car will stop 5m beyond the dog

View answer & explanation

Correct answer is B

F=ma
2000=800 x a
a = $\frac{2000}{800}$ → 2.5

V $^2$ =u $^2$ +2as
400=2 × 2.5 × S
S =400 ÷ 5 → 80
: 80 - 50 = 30
The car will stop 30m after hitting the dog

1,013.

All of the following frequencies are overtones of 320 Hz EXCEPT

960Hz

640Hz

520Hz

1280Hz

1600Hz

View answer & explanation

Correct answer is C

Overtones are frequency which are multiples of fundamental frequency

Fundamental frequency - f1 = 320Hz

Overtones 320 x 2 = 640Hz

320 x 3 = 960HZ

320 x 4 = 1280Hz

320 X 5 = 1600hZ