Refraction of a monochromatic ray through a prism when it goes through minimum deviation:

Applying the formula, v = λ x ν
where, v = velocity of sound =330 ms^-1
ν = frequency
λ = wavelength of sound
We have a range of frequencies from 20 Hz−20,000 Hz.
Hence, for frequency ν = 20 Hz, we have
330 = 20 ×λ
⇒λ = 330/20 = 16.5 m

For frequency ν = 20,000 , Hz, we have
330= 20000 ×λ
⇒ λ = 330/20000 = × 16.5 x10^-3 m

Distance between the plane and the radar, d = 300 km = 300,000 m
Velocity of radio waves, c = 3 x 10⁸ ms^-1
Waves from the radar will travel to the plane and then reflect and travel back
to the receiver of the radar. Hence, the total distance travelled by the waves
is 2d.
∴ 2d = c xt
∴ t = 2d/c
∴ 2 x300000 /3 x10⁸
∴ t = 2 x 10^-3 s = 2ms

(i) The frequency of stretched string related with its length as:

(ii) The frequency of stretched string is related to tension in the string as:
    v ∝ tension

This means frequency is inversely proportional to the length of the string and
directly proportional to its tension.

Specific resistance or resistivity (ρ), of a conductor, is defined as the resistance of a conductor of unit length and unit area of cross-section.
From the factors affecting the resistance of a conductor, the resistance is given by,

Its SI unit is ohm^-m
Specific resistance or resistivity is the characteristic property of the material of the conductor and depends only on the nature of the material and temperature.