# Plane waves of light of wavelength $$\lambda$$ are incident onto a convex lens, and the beam is brought to a focus. A plane slab of thickness $$t$$ having refractive indices $$\mu_1,~\mu_2$$ in the upper and lower halves is placed parallel to the incoming wavefronts. The phase difference between the wavefronts at the focus, coming from the upper and lower halves of the slab is:               1.  $$\dfrac{2 \pi}{\lambda}\left[\left(\mu_{1}-1\right) t+\left(\mu_{2}-1\right) t\right]$$ 2.  $$\dfrac{2 \pi}{\lambda}\left(\mu_{1}-\mu_{2}\right) t$$ 3.  $$\dfrac{2 \pi}{\lambda}\left(\dfrac{t}{\mu_{1}}-\dfrac{t}{\mu_{2}}\right)$$ 4.  $$\dfrac{2 \pi}{\lambda}\left(\dfrac{t}{\mu_{1}}+\dfrac{t}{\mu_{2}}\right)$$

Subtopic: Â Huygens' Principle |
From NCERT
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Light of wavelength $$\lambda$$ falls perpendicularly onto a single slit of width $$d$$. A diffraction maximum is formed at $$P$$ on a faraway screen placed parallel to plane of the slit. The first diffraction minimum is formed at $$Q,$$ as shown on the screen. Let $$C$$ be a 'point' so that it divides the slit $$AB$$ in the ratio $$\frac{AC}{CB}=\frac12,$$ i.e. $$AC$$ represents the upper $$\frac13^{rd}$$ of the slit. The total amplitude of the oscillation arriving from $$AC$$ at $$Q$$ is $$A_1$$ and from $$CB$$ at $$Q$$ is $$A_2$$.
Then:

1. $$2 A_{1}=A_{2}$$
2. $$A_{1}=2 A_{2}$$
3. $$\sqrt{2} A_{1}=A_{2}$$
4. $$A_{1}=A_{2}$$
Subtopic: Â Diffraction |
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Sound waves travel faster in water than in air. Imagine a plane sound wavefront incident at an angle $$\alpha$$ at the air-water interface; the refracted wavefront making an angle $$\beta$$ with the interface. Then,
 1 $$\alpha>\beta$$ 2 $$\beta>\alpha$$ 3 $$\alpha=\beta$$ 4 the relation between $$\alpha~\&~\beta$$ cannot be predicted.
Subtopic: Â Huygens' Principle |
From NCERT
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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 $$\dfrac{\pi}{2}.$$ The closest maximum to the central point is formed behind one of the slits. The separation between the slits is $$d,$$ and the slit to screen separation is $$D.$$ 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: Â Young's Double Slit Experiment |
From NCERT
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A linearly polarized monochromatic light of intensity $$10$$ lumen is incident on a polarizer. The angle between the direction of polarization of the light and that of the polarizer such that the intensity of output light is $$2.5$$ lumen is:
1. $$60^\circ$$
2. $$75^\circ$$
3. $$30^\circ$$
4. $$45^\circ$$
Subtopic: Â Polarization of Light |
Â 66%
From NCERT
NEET - 2022
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A monochromatic light of frequency $$500$$ THz is incident on the slits of a Young's double slit experiment. If the distance between the slits is $$0.2$$ mm and the screen is placed at a distance $$1$$ m from the slits, the width of $$10$$ fringes will be:
1. $$1.5$$ mm
2. $$15$$ mm
3. $$30$$ mm
4. $$3$$ mm

Subtopic: Â Young's Double Slit Experiment |
Â 56%
From NCERT
NEET - 2022
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In a Young's double-slit experimental setup, $$240$$ fringes are observed to be formed in a region of the screen when light of wavelength $$450$$ nm is used. If the wavelength of light is changed to $$600$$ nm, the number of fringes formed in the same region will be:
 1 $$135$$ 2 $$180$$ 3 $$320$$ 4 $$428$$
Subtopic: Â Young's Double Slit Experiment |
Â 71%
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Young's double-slit experiment is conducted with the light of wavelength, $$\lambda=4500~\mathring A$$ and $$400$$ fringes are observed in a $$10$$ cm region on the screen. The apparatus is immersed in a clear liquid of refractive index $$\mu=2.$$ The number of fringes observed will be:
1. $$400$$
2. $$800$$
3. $$200$$
4. $$1600$$
Subtopic: Â Young's Double Slit Experiment |
Â 70%
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After passing through a polarizer, a linearly polarized light of intensity $$I$$ is incident on an analyser making an angle of $$30^\circ$$ with the axes of the polariser. The intensity of light emitted from the analyser will be:
1. $$\dfrac{I}{2}$$
2. $$\dfrac{I}{3}$$
3. $$\dfrac{3I}{4}$$
4. $$\dfrac{2I}{3}$$
Subtopic: Â Polarization of Light |
Â 79%
From NCERT
NEET - 2022
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If the screen is moved away from the plane of the slits in Young's double slit experiment, then the:
1. angular separation of the fringes increases.
2. angular separation of the fringes decreases.
3. linear separation of the fringes increases.
4. linear separation of the fringes decreases.
Subtopic: Â Young's Double Slit Experiment |
Â 63%
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NEET - 2022
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