Pakistan MCQs

A converging lens brings paraxial parallel rays to its principal focus.
The focal length is positive under the common sign convention.

Standing waves form from superposition of opposite traveling waves.
Nodes remain at zero displacement.

Higher-frequency sound is perceived as higher pitch.
Pitch perception is related to but not identical with frequency.

Greater wave amplitude generally means greater intensity.
Perceived loudness is also frequency-dependent.

Approach raises observed frequency, while separation lowers it.
The effect occurs for sound and electromagnetic waves.

Frequency is cycles divided by time.
20/5 = 4 Hz.

Period is the reciprocal of frequency.
T=1/5 = 0.2 s.

Use v=fλ.
λ=12/3 = 4 m.

Wave speed is v=fλ.
V=8×2.5 = 20 m/s.

Damping removes mechanical energy from an oscillator.
Friction and drag are common causes.

Frequency is speed divided by wavelength.
F=340/0.68 = 500 Hz.

Mechanical waves transfer energy through oscillating matter.
Sound and water waves are examples.