Tag: travelling waves

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Questions Related to travelling waves

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

Ocean waves of time period $0.01$ second have a speed $15 m/s$. What is the adjacent crest and the trough is:

  1. $15 \times 10^{-2} m$
  2. $7.5 \times 10^{-2} m$
  3. $3.25 \times 10^{-2} m$
  4. $30 \times 10^{-2} m$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The distance between a crest and an adjacent trough is half the wavelength (lambda/2). Wavelength = speed * time period = 15 * 0.01 = 0.15 m. Half the wavelength is 0.075 m, which is 7.5 * 10^-2 m.

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

The velocity of light in glass whose refractive index w.r.t air is $1.5$ is $2 \times 10^8 \,m/s$. In a certain liquid, the velocity of light is found to be $2.5 \times 10^8 \,m/s$. The refractive index of the liquid w.r.t air is

  1. $0.8$
  2. $0.9$
  3. $1.2$
  4. $1.33$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Velocity of light in glass $(v _1)=2\times 10^8 m/s$
Refractive index of glass $(\eta _1)=1.5$
w.r.t air
Velocity of light in certain $2\times 10^8\ m/s$
liquid $(v _2)$
Let refractive index of certain $=\eta _g$
liquid w.r.t air
Using formula,
$Refractive\ index=\dfrac{Velocity\ of\ light}{Velocity\ of\ light\ in\ med}$
we get
$\dfrac{\eta _1}{\eta _2}=\dfrac{V _2}{V _1}$
$\eta _2=\dfrac{\eta _1 V _1}{V _2} $
$\eta _2=\dfrac{31.5\times 2\times 10^8}{52.5\times 10^8}$
$\eta _2=\dfrac{6}{5}=1.2$
$\therefore$ Refractive index of certain liquid$=1.2$
Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

A transverse wave travelling on a taut string is represented by $y = 0.01 \sin 2 \pi ( 10 t - x )$ where y and x are in metre and t is in second. Then

  1. The speed of the wave is 10 m/s.
  2. Closest points on the string which differ in phase by $60^o$ are $\dfrac16\ m$ apart.
  3. Maximum particle speed is $\frac { \pi } { 5 } { m } / { s }$
  4. The phase of a certain point on the string changes by $120 ^ { \circ }$ is $\dfrac1{20} $seconds
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

What is the phase difference between two successive crests in the wave?

  1. $\pi$
  2. $\frac{\pi}{2}$
  3. $2\pi$
  4. $4\pi$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Phase difference between any two particles in a wave determines lack of harmony in the vibrating state of two particles, ie, how far one particle leads the other or lags behind the other. 
Relation of path difference and phase difference is given by
$\Delta \phi=\frac{2\pi}{\lambda}\times \Delta x$
where $\Delta x$ is path difference. 
But path difference between two crests
$\Delta x=\lambda$
Hence, $\Delta  \phi = \frac{2\pi}{\lambda}\times \lambda =2\pi$ 

Multiple choice physics properties of waves longitudinal and transverse waves travelling waves types of waves

The wave produced by a motor boat sailing in water are

  1. Transverse

  2. Longitudinal

  3. Longitudinal and Transverse

  4. Stationary
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The waves produced by a motorboat sailing in water are of both transverse and longitudinal type. Transverse waves are produced on the surface and longitudinal waves are produced deep inside the water.