A parallel beam of light of wavelength $\lambda$ is incident normally on a single slit of width $d,$ and a pattern of maxima and minima are observed on a screen placed far behind the slit. The first minimum (nearest to the central maximum) is formed at an angle $\theta,$ where $\sin\theta=$

1. $\dfrac{\lambda}{d}$ 2. $\dfrac{\lambda}{2d}$

3. $\dfrac{2\lambda}{d}$ 4. $\dfrac{\lambda}{4d}$

Subtopic: Diffraction |

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Q20:

Two waves from coherent sources meet at a point in a phase difference of

ϕ

$\phi$ and path difference

Δ x .

$\Delta x.$ Both waves have same intensities

I_{0} .

$I_0.$ Based on this information, match Column-I and Column-II.

	Column-I		Column-II
(a)	If ${\Delta x}=\dfrac{\lambda}{3}$	(p)	resultant intensity will be $3I_0$
(b)	If $\phi = 60^{\circ}$	(q)	resultant intensity will be $I_0$
(c)	If ${\Delta x}=\dfrac{\lambda}{4}$	(r)	resultant intensity will be zero
(d)	If $\phi = 90^{\circ}$	(s)	resultant intensity will be $2I_0$

1.	a(q), b(p), c(s), d(s)
2.	a(s), b(p), c(s), d(q)
3.	a(q), b(s), c(s), d(p)
4.	a(s), b(r), c(q), d(r)

Subtopic: Superposition Principle |

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Q21:

In a Young's double slit interference experiment the fringe pattern is observed on a screen placed at a distance

D

$D$ from the slits. The slits are separated by a distance

d

$d$ and are illuminated by monochromatic light of wavelength

λ

$\lambda$ . The minimum distance from the central point where intensity falls to

\frac{1}{4} t h

$\dfrac{1}{4}{th}$ of the maximum value:

1.	$\dfrac{D\lambda}{2d}$	2.	$\dfrac{D\lambda}{3d}$
3.	$\dfrac{D\lambda}{4d}$	4.	$\dfrac{D\lambda}{5d}$

Subtopic: Young's Double Slit Experiment |

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Q18:

Young's double-slit experiment is conducted with the light of wavelength,

λ = 4500 \overset{˚}{A}

$\lambda=4500~\mathring A$ and

400

$400$ fringes are observed in a

10

$10$ cm region on the screen. The apparatus is immersed in a clear liquid of refractive index

μ = 2.

$\mu=2.$ The number of fringes observed will be:
1.

400

$400$
2.

800

$800$
3.

200

$200$
4.

1600

$1600$

Subtopic: Young's Double Slit Experiment |

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Q17:

In a Young's double-slit experimental setup,

240

$240$ fringes are observed to be formed in a region of the screen when light of wavelength

450

$450$ nm is used. If the wavelength of light is changed to

600

$600$ nm, the number of fringes formed in the same region will be:

1.	$135$	2.	$180$
3.	$320$	4.	$428$

Subtopic: Young's Double Slit Experiment |

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Q16:

Electrons (mass

m

$m$ ) moving with a velocity

v

$v$ are incident normally onto a single slit of width

d,

$d,$ and are detected on a screen placed at a distance

D

$D$ behind the slit. The central point on the screen where most of the electrons are detected is

O .

$O.$ The closest point to

O

$O$ where no electrons are detected is

X .

$X.$ Then

O X

$OX$ equals:

1.	$\dfrac{hD}{mvd}$	2.	$\dfrac{hD}{2mvd}$
3.	$\dfrac{2hD}{mvd}$	4.	$\dfrac{3hD}{2mvd}$

Subtopic: Diffraction |

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Q15:

Young's double-slit experiment is performed with identical slits separated by a distance

d,

$d,$ and with light of wavelength

λ .

$\lambda.$ The screen is placed at a point which is at a distance

D

$D$ from the double-slit, as usual. A convex lens of focal length

f

$f$ is inserted between the double-slit and the screen, very close to the double slit. The screen is adjusted (i.e. the value of

D

$D$ is slowly varied) until a clear interference pattern is formed. The fringe width equals:

1.	$\dfrac{\lambda f}{d}$	2.	$\dfrac{2\lambda f}{d}$
3.	$\dfrac{\lambda f}{2d}$	4.	$\dfrac{\lambda f}{d\sqrt2}$

Subtopic: Young's Double Slit Experiment |

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Q14:

Young's double-slit experiment is conducted with light of an unknown wavelength, the waves arriving at the central point on the screen are found to have a phase difference of

\frac{π}{2} .

$\dfrac{\pi}{2}.$ The closest maximum to the central point is formed behind one of the slits. The separation between the slits is

d,

$d,$ and the slit to screen separation is

D .

$D.$ The longest wavelength for this to happen is:

1.	$\dfrac{2d^2}{D}$	2.	$\dfrac{2d^2}{3D}$
3.	$\dfrac{d^2}{2D}$	4.	$\dfrac{d^2}{6D}$

Subtopic: Young's Double Slit Experiment |

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Q13:

Sound waves travel faster in water than in air. Imagine a plane sound wavefront incident at an angle

α

$\alpha$ at the air-water interface; the refracted wavefront making an angle

β

$\beta$ with the interface. Then,

1.	$\alpha>\beta$
2.	$\beta>\alpha$
3.	$\alpha=\beta$
4.	the relation between $\alpha~\&~\beta$ cannot be predicted.

Subtopic: Huygens' Principle |

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Q12:

In a Young's double-slit experiment with identical slits (of slit separation-

d,

$d,$ slit to screen distance

D

$D$ ), the phase difference between the waves arriving at a point just opposite to one of the slits is

\frac{π}{2} .

$\dfrac{\pi}{2}.$ The source is placed symmetrically with respect to the slits. The wavelength of light is:

1.	$\dfrac{2d^2}{D}$	2.	$\dfrac{d^2}{2D}$
3.	$\dfrac{d^2}{D}$	4.	$\dfrac{D^2}{d}$

Subtopic: Young's Double Slit Experiment |

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1.	$\dfrac{\lambda}{d}$	2.	$\dfrac{\lambda}{2d}$
3.	$\dfrac{2\lambda}{d}$	4.	$\dfrac{\lambda}{4d}$

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