Nootan Solutions Optical Instruments ISC Class-12 Physics Ch-18 ISC Class-12 Physics Nageen Prakashan Numericals. Step by step Solutions of Kumar and Mittal ISC Physics Class-12 Nageen Prakashan Numericals Questions. Visit official Website CISCE for detail information about ISC Board Class-12 Physics.

## Nootan Solutions Optical Instruments ISC Class-12 Physics Ch-18

 Board ISC Class 11 Subject Physics Publication Nageen Prakashan Writer Kumar and Mittal Vol 2nd Book Name Nootan Chapter-18 Optical Instruments Topics Solution of Numericals Questions Page-Number 774,775

### Nootan Solutions Optical Instruments

(Ch-18 ISC Class-12 Physics Nageen Prakashan Numericals)

1. Ray Optics or Geometrical Optics In this optics, the light is considered as a ray which travels in a straight line. It states that for each and every object, there is an image.
2. Reflection Reflection is the phenomenon of changing the path of light without any change in the medium.
3. Reflection of Light The returning back of light in the same medium from which it has come after striking a surface is called reflection of light.
4. Laws of Reflection
Two laws of reflection are given as below:
(i) The angle of incidence i is equal to the angle of reflection r.
i.e. ∠i = ∠r.
(ii) The incident ray, reflected ray and normal to the reflecting surface at the point of incidence all lie in the same plane. 5. Total number of images formed by two plane mirrors inclined at an angle θ with each other is given by 6. Reflecting surface of a spherical mirror is a part of a hollow sphere. Spherical mirrors are of two types, (i) Concave spherical mirror (ii) Convex spherical mirror. 7. Sign Convention All measurements should be taken from pole of mirror. All measurements along the direction of incident ray will be positive and opposite to incident ray are negative. All the measurements for the distances above the principal axis are taken as positive and below the principal axis are taken as negative.
8. For a real object, u is negative whereas v is negative for real image and positive for virtual image.

9. Magnification (m) It is negative corresponding to real image and positive for virtual image.
10. Refraction The phenomenon of changing in the path of light as it goes from one medium to another is called refraction.
11. Laws of Refraction : Two laws of refraction are given as below:
(a) The incident ray, refracted ray and the normal to the refracting surface at the point of incidence lie in the same plane.
(b) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for the two given media. This constant is denoted by n and is called the relative refractive index.
n = sin i/sin r (Snell’s law)
where, n is refractive index of the second medium when first medium is air.

12. Total Internal Reflection : (TIR) When a ray of light travelling from denser medium to rarer medium is incident at the interface of two medium at an angle greater than the critical angle for the two media, the ray is totally reflected back to denser medium. This phenomenon is called Total Internal Reflection. It occurs only when angle of incidence in denser medium is greater (not equal) than critical angle, i.e. i> i c. Nootan Solutions Optical Instruments

### (Ch-18 ISC Class-12 Physics Nageen Prakashan Numericals)

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