NEET UG Physics Practice Paper – Ray Optics (Set 12)

NEET UG Physics Notes – Ray Optics (Set 12)

Ray Optics is one of the most important and scoring chapters in NEET UG Physics. It deals with the behavior of light in terms of rays and includes concepts like reflection, refraction, lenses, mirrors, prisms, and optical instruments. Questions are mostly formula-based and conceptual, making it a high-scoring topic.

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1. Reflection of Light

Reflection occurs when light bounces back from a surface.

Laws of Reflection:

1. Angle of incidence = Angle of reflection
2. Incident ray, reflected ray, and normal lie in the same plane

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2. Types of Mirrors

Plane Mirror:

• Forms virtual, erect image
• Image distance = object distance
• Magnification = 1

Concave Mirror:

• Can form real or virtual images
• Used in shaving mirrors, headlights

Convex Mirror:

• Always forms virtual, erect, diminished image
• Used as rear-view mirrors

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3. Mirror Formula

$$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$$f1​=v1​+u1​

Magnification:

$$m = \frac{v}{u}$$m=uv​

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4. Refraction of Light

Refraction is bending of light when it passes from one medium to another due to change in speed.

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5. Snell’s Law

$$n_1 \sin\theta_1 = n_2 \sin\theta_2$$n1​sinθ1​=n2​sinθ2​

Refractive Index:

$$n = \frac{c}{v}$$n=vc​

• Higher $n$n → slower light

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6. Total Internal Reflection (TIR)

Occurs when light travels from denser to rarer medium and:

• Angle of incidence > critical angle

Critical Angle Condition:

$$\sin C = \frac{1}{n}$$sinC=n1​

Applications:

• Optical fiber
• Prism
• Mirage

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7. Lenses

Convex Lens:

• Converging lens
• Can form real or virtual images

Concave Lens:

• Diverging lens
• Always forms virtual image

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8. Lens Formula

$$\frac{1}{f} = \frac{1}{v} – \frac{1}{u}$$f1​=v1​−u1​

Magnification:

$$m = \frac{v}{u}$$m=uv​

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9. Power of Lens

$$P = \frac{1}{f}$$P=f1​

Unit:

• Diopter (D)

Lens Combination:

$$P_{total} = P_1 + P_2$$Ptotal​=P1​+P2​

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10. Image Formation

Real Image:

• Inverted
• Can be obtained on screen

Virtual Image:

• Erect
• Cannot be obtained on screen

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11. Prism

A prism refracts light and causes deviation.

Angle of Deviation:

• Depends on refractive index

Minimum Deviation:

• Occurs when path is symmetric

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12. Dispersion of Light

Splitting of white light into its component colors.

Order:

• VIBGYOR

Key Points:

• Red: longest wavelength
• Violet: shortest wavelength

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13. Speed of Light in Medium

$$v = \frac{c}{n}$$v=nc​

Insight:

• Higher refractive index → slower light

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14. Optical Fiber

Works on Total Internal Reflection

Uses:

• Communication
• Medical imaging

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15. Important NEET Formulas

• $1/f = 1/v + 1/u$1/f=1/v+1/u (mirror)
• $1/f = 1/v – 1/u$1/f=1/v−1/u (lens)
• $m = v/u$m=v/u
• $n = c/v$n=c/v
• $P = 1/f$P=1/f

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16. Common Mistakes

❌ Confusing mirror and lens formulas
❌ Wrong sign convention
❌ Forgetting TIR conditions
❌ Mixing real and virtual images

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17. Quick Revision Tips

• Practice ray diagrams
• Remember sign conventions
• Focus on lens & mirror formulas
• Prism and TIR are frequently asked

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Conclusion

Ray Optics is a high-weightage and easy scoring chapter if concepts are clear.

Focus on:

• Reflection & refraction
• Lens & mirror formulas
• TIR & prism
• Image formation

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