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Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

In a bi-prism experiment fifth dark fringes are obtained at a point. If a thin transparent film is placed in the path of one of waves, then seventh bright fringe is obtained at the same point. The thickness of the film in terms of wavelength $X$ and refractive index $\mu$ will be

  1. $\displaystyle\frac{1.5\lambda}{(\mu-1)}$

  2. $\displaystyle{1.5}{(\mu-1)\lambda}$

  3. $\displaystyle{2.5}{(\mu-1)\lambda}$

  4. $\displaystyle\frac{2.5\lambda}{(\mu-1)}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For 5th dark fringe to be obtained at the point, the path difference of the beams at that point =$\dfrac{9\lambda}{2}$.

For 7th bright fringe to be obtained at the same point, the new path difference of the beams at that point =$7\lambda$.
Due to insertion of the film of thickness $t$, path difference added to the beam=$t(\mu-1)$
Hence, $\dfrac{9\lambda}{2}+t(\mu-1)=7\lambda$
Hence, $t=\dfrac{2.5\lambda}{(\mu-1)}$

Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

Which of the following formulae is incorrect in a bi-prism?

  1. $d=\sqrt{d _1d _2}$

  2. $d=2a(\mu-1)a$

  3. $d=\displaystyle\frac{D\lambda}{\beta}$

  4. $d=\displaystyle\sqrt\frac{d^2 _1}{d _2}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

If $d _{1}$, $d _{2}$ are the distances of two virtual sources from the central axis, the average $d$ is given by

 $d=\sqrt{d _{1}d _{2}}$.

Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

In Fresnel's bi-prism experiment, the coherent sources are obtained by

  1. interference

  2. reflection

  3. refraction

  4. total internal reflection
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Fresnel bi-prism, light from the single source are made into two virtual sources on passing it through the bi-prism due to refraction in prism, so that the two sources acts as a coherent sources

Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

Which of the following statements is correct?

  1. Diffraction is because of interference of light from same sources whereas interference is due to light form two isolated sources.

  2. Diffraction is due to interaction of light from same wave fronts whereas interference is due to interaction of two waves derived from the same source.

  3. Diffraction is due to interference of waves derived from the same source whereas interference is bending of light from the same source.

  4. Diffraction is due to reflected waves whereas interference is due to transmitted waves from a source.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a same source is present, it might give different colours depending on the path difference between the interfering rays from the source.

However when two completely different sources are present, they interfere due to path difference between them and give the interference pattern. For example, Young' double slit experiment.

Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

In a Fresnel's biprism experiment the two positions of lens separation between the slits as $16cm$ and $9cm$ respectively. The true distance of separation between the slits is 

  1. $10cm$

  2. $12cm$

  3. $14cm$

  4. $15cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the displacement method for a biprism, the distance between the virtual slits d = sqrt(d1 * d2). Here, d = sqrt(16 * 9) = sqrt(144) = 12 cm.

Multiple choice physics superposition of waves difference between interference and diffraction explaining wave phenomena diffraction

In Young's experiment fourth bright fringe produced by light of $5000\overset{o}{A}$ superposes on the fifth bright fringe of an unknown wavelength. The unknown wavelength is _________$\overset{o}{A}$.

  1. $4000$

  2. $6000$

  3. $5000$

  4. $8000$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$ \beta = \dfrac{ \lambda \times D}{d} $
$4\beta _1=5\beta _2$
$4\times 5000\dfrac{D}{d}=5\times \lambda\dfrac{D}{d}$
$\lambda =4000\overset{o}{A}$.
Multiple choice physics wave optics difference between interference and diffraction explaining wave phenomena diffraction

A monochromatic plane wave of speed c and wavelength $\lambda$ is diffracted at a small aperture. The diagram illustrates successive wave fronts.
After what time will some portion of the wave front GH reach point P?

  1. $\dfrac{3\lambda}{2c}$

  2. $\dfrac{2\lambda}{c}$

  3. $\dfrac{3\lambda}{c}$

  4. $\dfrac{4\lambda}{c}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The distance between two consecutive lines(wavefronts ) ia $\lambda$.
So, wavefront XY is separated by a distance of 3λ from the wavefront that has reached point P.

Distance that needs to be travelled = $3\lambda$
Speed of light = $c$

Speed =$\dfrac{Distance}{time}$
Time = $\dfrac{Distance}{Speed}$
        = $\dfrac{3\lambda}{c}$
Multiple choice physics properties of waves difference between interference and diffraction explaining wave phenomena diffraction

Diffraction is a term used to describe one aspect of wave behaviour.
What does diffraction make possible?

  1. The ability to hear around corners

  2. The ability to hear high frequency and low frequency sound waves

  3. The ability to hear loud and quiet sounds

  4. The ability to hear sound through a brick wall
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Diffraction is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening. If the opening is much larger than the light's wavelength, the bending will be almost unnoticeable.

So, diffraction makes the sound wave hear around corner.