Class 11th

This is a multiple choice answer as classified in NCERT Exemplar

(b) Amplitude of reflected wave

A_f= $\frac{2}{3}*A_i$ =2 (0.6)/3=0.4 units

Equation of incident wave

Y_i=0.6sin2 $\pi \left(t-\frac{x}{2}\right)$

For reflected wave 

y_r=A_rsin2 $\pi$ (t+x/2+ $\pi$ )

Y_r=-0.4sin2 $\pi \left(t+\frac{x}{2}\right)$

This is a multiple choice answer as classified in NCERT Exemplar

(d) Due to compression and rarefactions density of the medium changes.at compressed regions density is maximum and at rarefactions density is minimum

As density is changing so boyle, s law not obeyed

Bulk modulus remains same

The time of compression and rarefaction is too small so no transfer of heat.

This is a multiple choice answer as classified in NCERT Exemplar

(c) When mechanical transverse wave propagates through a medium, the constituents of the medium oscillate perpendicular to wave motion causing change in shape. That is each element of the medium is subjected to shearing stress. Solids and strings have shear, that is why tey bear stress. But in fluids there is no fixed shape so transverse waves does not formed in fluid.

This is a multiple choice answer as classified in NCERT Exemplar

(b) Propagation of longitudinal waves through a medium leads to transmission of energy through the medium without matter being transmitted. So no movement of energy and matter hence momentum

This is a multiple choice answer as classified in NCERT Exemplar

(c) Speed of sound wave in a medium v $\propto \sqrt[]{T}$

Clearly when temperature changes speed also changes

As v= $v\lambda$ as frequency remains constant and speed changes so wavelength changes

This is a multiple choice answer as classified in NCERT Exemplar

(c) Due to presence of moisture density of air decreases.

As we know speed of sound in air v= $\sqrt[]{\frac{\gamma P}{\rho }}$

So v $\propto \frac{1}{\sqrt[]{\rho }}$

v_2/v₁= $\sqrt[]{\frac{{\rho }_2}{{\rho }_1}}$

_{$\rho$ 2} (moist air)< $\rho$ ₁ (dry air)

So v₂>v₁

So speed of sound wave increases with increase in humidity

This is a multiple choice answer as classified in NCERT Exemplar

(c) Let frequency of the two will be  $vandv\text{'}$  and it is same in both medium

So v/ $\lambda$ = v'/ $\lambda$

$\lambda \text{'}$ = v' $\lambda$ /v

$\lambda \text{'}$ = 2v $\lambda$ /v=2 $\lambda$

Where $\lambda$ and $\lambda$ ' and v and v' are wavelength and speeds of first and second medium respectively

This is a multiple choice answer as classified in NCERT Exemplar

(b) Water waves produced by a motorboat are both longitudinal and transverse because it produce both lateral and transverse wave In the medium.

This is a short answer type question as classified in NCERT Exemplar

Let there are n number of loops in the string

length corresponding each loop is $\frac{\lambda }{2}$

So we can write L= $\frac{n\lambda }{2}$

$\lambda =\frac{2L}{n}$

v/ $v$ =2L/n

so frequency $v=\frac{n}{2L}$ v= $\frac{n}{2L}\sqrt[]{\frac{T}{\mu }}$

v $\propto n$

so $v_1:v_2:v_3:v_4=n_1:n_2:n_3:n_4$

= 1:2:3:4

This is a short answer type question as classified in NCERT Exemplar

consider the frequency of tuning fork= 512Hz

(a) L= $\frac{\lambda }{4}$

$\lambda =4L$

V= $v\lambda$ = 512 $*4*17*{10}^{-2}$

= 348.16m/s

(b) we know that v $\propto \sqrt[]{T}$

$\frac{V_{20}}{V_0}$ = $\sqrt[]{\frac{273+20}{273}}=\sqrt[]{\frac{293}{273}}$

$\frac{V_{20}}{V_0}=\sqrt[]{1.073}=1.03$

V_o= $\frac{V_{20}}{1.03}=\frac{348.16}{1.03}=338m/s$

(c) Resonance will be observed at 17cm length of air column only intensity of sound heard may be greater due to more complete reflection of the sound waves at the mercury surface because mercury is more denser than water.