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JAMB Physics Past Questions & Answers - Page 156

776.

A radioactive source emits X–rays of very short wavelength (10 -13m ). what is the frequency of these rays?

A.

2 × 1018HZ

B.

3 × 10 19HZ

C.

3 × 1021HZ

D.

3 × 10-19HZ

Correct answer is C

Wavelength(λ)=1013m

Speed of X-ray = speed of light C=3×108m/s

Frequently (f) = ?

Using V = f\lambda (or (– f π for electromagnetic wave)

f = \frac{c}{\lambda} = 3 \times 10^{8} ÷ 10^{-13} = 3 \times 10^{8} \times 10^{13}

= 3 \times 10^{8} \times 10^{13}

= 3 \times 10^{21}Hz

777.

The symbol −10X used to represent which of the particles?

A.

Proton

B.

Neutron

C.

Electrons

D.

Atoms

Correct answer is C

Electron: A sub–atomic particle haring a negative charge and orbiting the nucleus (note: the symbol 0–1e represent the particle of an electrons.)

778.

The optical instrument which is suitable for viewing a nearby objects is ………..?

A.

Telescope

B.

sextant

C.

microscope

D.

periscope

Correct answer is C

Microscope is used for nearby object

779.

If an object whose mass is 3kg moves in a circular path of a radius 0.7m, records a speed at 2m/s. What is the result of the angular velocity?

A.

4 rads–1

B.

1rads–1–1

C.

3–1rads–1

D.

4rads–1–1

Correct answer is C

M= 3kg, r = 0.7m, v = 2m/s

v = wr

w = angular velocity

r = radius in an tangential circular

v = speed of an object

W = V/δ = 2/ 0.7 = 2.85

W = 2.853rads–1 (total interest whole number)

W = &approx.; 3rads–1Angular velocity (w) = 3rads–1

780.

A structural engineer stood on a top of a building releasing a light and heavy object to the ground which of the following statement is true?(Neglect Air Resistance)

A.

Both the light and heavy subject reach the ground at the same time

B.

The light object get to the ground first before the heavy object

C.

The heavy object to the ground first before the light object

D.

None get to the ground first

Correct answer is A

(Neglect of Air resistance)

Note: Both objects reach the ground at the same time