NEET UG Physics Practice Paper – Wave Optics (Set 13)

Attempt all 30 questions. Click submit to see your score and detailed explanations.

1. Interference of light occurs due to:

Superposition of waves
Reflection
Refraction
Polarization

2. Condition for constructive interference is:

\(n\lambda\)
\((2n+1)\lambda/2\)
\(n\lambda/2\)
Zero

3. Young’s double slit experiment demonstrates:

Wave nature of light
Particle nature
Nuclear force
Electric field

4. Fringe width is given by:

\(\lambda D/d\)
\(d/\lambda D\)
\(D/\lambda\)
\(d\lambda\)

5. Coherent sources have:

Constant phase difference
Same amplitude
Same speed
Same intensity

6. Diffraction is:

Bending of light
Reflection
Refraction
Dispersion

7. Diffraction is prominent when:

Slit ≈ wavelength
Slit >> wavelength
Slit << wavelength
None

8. Central maximum in diffraction is:

Widest
Narrowest
Same
Zero

9. Polarization proves light is:

Transverse
Longitudinal
Both
None

10. Brewster’s law:

tanθ = n
sinθ = n
cosθ = n
None

11. Intensity ∝

A²
A
A³
None

12. Path difference unit:

m
s
Hz
None

13. Phase unit:

rad
m
s
None

14. Fringe width increases with:

λ
d
none
zero

15. Fringe width decreases with:

d
λ
none
zero

16. Light speed:

3×10⁸
10⁶
10⁵
none

17. Interference pattern:

equally spaced
random
none
zero

18. Diffraction minima:

a sinθ = nλ
λ
none
zero

19. Central maxima:

brightest
dim
none
zero

20. Polarizer:

reduces intensity
increases
none
zero

21. Unpolarized light:

random vibration
fixed
none
zero

22. Interference needs:

coherence
reflection
none
zero

23. Diffraction width:

∝1/slit
∝slit
none
zero

24. Wavelength unit:

m
s
Hz
none

25. Max intensity:

in phase
out
none
zero

26. Min intensity:

out phase
in phase
none
zero

27. Fringe width ∝

D
d
none
zero

28. Light nature:

dual
wave
particle
none

29. Diffraction pattern:

unequal fringes
equal
none
zero

30. Interference pattern:

equal fringes
unequal
none
zero

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NEET UG Physics Notes – Wave Optics (Set 13)

Wave Optics explains the wave behavior of light and is a high-weightage chapter in NEET UG. Most questions are conceptual but straightforward if formulas and conditions are clear. The chapter mainly includes interference, diffraction, and polarization.

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1. Wave Nature of Light

Light behaves like a wave in certain phenomena such as:

• Interference
• Diffraction
• Polarization

👉 These phenomena cannot be explained using particle theory alone.

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2. Principle of Superposition

When two waves overlap, the resultant displacement is the sum of individual displacements.

Result:

• Constructive interference (bright fringe)
• Destructive interference (dark fringe)

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3. Interference of Light

Interference is the redistribution of intensity due to overlapping waves.

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4. Conditions for Interference

Constructive Interference:

$$\text{Path difference} = n\lambda$$Path difference=nλ

Destructive Interference:

$$\text{Path difference} = \frac{(2n+1)\lambda}{2}$$Path difference=2(2n+1)λ​

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5. Young’s Double Slit Experiment (YDSE)

Fringe Width:

$$\beta = \frac{\lambda D}{d}$$β=dλD​

Where:

• $\lambda$λ = wavelength
• $D$D = distance to screen
• $d$d = slit separation

Key Observations:

• Fringes are equally spaced
• Central fringe is brightest

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6. Coherent Sources

Sources are coherent if:

• Same frequency
• Constant phase difference

👉 Essential condition for interference.

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7. Factors Affecting Fringe Width

$$\beta \propto \frac{\lambda D}{d}$$β∝dλD​

Increases with:

• Wavelength
• Distance between slit and screen

Decreases with:

• Slit separation

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8. Diffraction of Light

Diffraction is the bending of light around edges or apertures.

Key Condition:

• Significant when slit width ≈ wavelength

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9. Single Slit Diffraction

Minima Condition:

$$a \sin\theta = n\lambda$$asinθ=nλ

Important Features:

• Central maximum is widest and brightest
• Intensity decreases away from center

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10. Interference vs Diffraction

Feature	Interference	Diffraction
Source	Two sources	Single slit
Fringe Width	Equal	Unequal
Intensity	Uniform	Decreasing

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11. Polarization of Light

Polarization restricts vibrations of light in one direction.

Conclusion:

• Light is a transverse wave

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12. Polarizers

Devices that produce polarized light.

Effect:

• Reduce intensity
• Used in sunglasses, LCDs

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13. Brewster’s Law

$$\tan\theta_B = n$$tanθB​=n

At Brewster Angle:

• Reflected light becomes completely polarized

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14. Intensity of Light

$$I \propto A^2$$I∝A2

Where:

• $A$A = amplitude

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15. Path Difference and Phase Difference

$$\Delta \phi = \frac{2\pi}{\lambda} \times \text{path difference}$$Δϕ=λ2π​×path difference

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16. Diffraction Pattern Characteristics

• Central maximum is brightest
• Width inversely proportional to slit size
• Side maxima have lower intensity

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17. Important NEET Formulas

• $\beta = \frac{\lambda D}{d}$β=dλD​
• $a\sin\theta = n\lambda$asinθ=nλ
• $I \propto A^2$I∝A2
• $\tan\theta_B = n$tanθB​=n

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18. Common Mistakes

❌ Confusing interference and diffraction
❌ Forgetting condition for coherence
❌ Mixing up constructive and destructive conditions
❌ Ignoring units

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19. Quick Revision Tips

• Fringe width formula is very important
• Central maximum is always widest
• Diffraction depends on slit width
• Polarization confirms transverse nature

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Conclusion

Wave Optics is a conceptual but easy scoring chapter.

Focus on:

• Interference formulas
• Diffraction conditions
• Polarization concepts

👉 With proper practice, you can score full marks from this chapter in NEET.