JAMB Physics Past Questions & Answers - Page 181

901.

An object is positioned between two plane mirrors inclined at right angles to each other. The object is 1 unit distance from each mirror, the number of images formed is

A.

1

B.

2

C.

3

D.

4

E.

5

Correct answer is C

No. of image formed = \(\frac{360}{\theta}\) - 1

= \(\frac{360}{90}\) - 1

= 3 images

902.

The visible part of light consists of the following colours

A.

red, indigo, infra-red, violet, yellow, green and blue

B.

red, green, blue, violet, indigo, orange and yellow

C.

blue, ultra-violet, infra-red, red, yellow, indigo, violet,green and orange

D.

infra-red and ultra-violet

E.

red, orange, yellow, green, blue, indigo and infra-red

Correct answer is B

The visible colors of white light is given by the acronym: ROYGBIV which stands for Red, Orange, Yellow, Green, Blue, Indigo and Violet.

903.

An object 1cm high placed on the axis 15cm from a converging lens forms an image 30cm from the lens. The size of the image is

A.

0.5cm

B.

1.5cm

C.

3cm

D.

2.5cm

E.

2cm

Correct answer is E

\(\frac{\text{image distance}}{\text{object distance}}\) = \(\frac{\text{image height}}{\text{object height}}\)

\(\frac{30}{15}\) = \(\frac{\text{image height}}{1}\)

image height = 2cm

904.

A herdsman yelling out to fellow herdsman heard his voice reflected by cliff 4s later. What is the velocity of sound in air if the cliff is 680m away?

A.

170ms-1

B.

136ms-1

C.

340ms-1

D.

680ms-1

E.

510ms-1

Correct answer is C

Velocity = \(\frac{\text{distance}}{\text{time}}\)

echo time = halt total time

= \(\frac{1}{2}\) x 4 = 25

velocity = \(\frac{680}{2}\)

= 340ms-1

905.

Two boys are communicating with each other by stretching a string passing through a hole punched in the bottom of each of two tin cans. The physical principle employed is that sound travels

A.

mainly through air

B.

fainter in stretched string

C.

faster through gases than in solids and liquids

D.

with greater ease through a string than in air

E.

none of the above is correct

Correct answer is D

No explanation has been provided for this answer.