 # Geometrical Optics Formulae for NEET

1. Laws of Reflection of light • The incident ray, the refracted ray, and normal lie on the same plane
• Snells law

sin i/sin r = constant

2. Relative refractive index

1n2 = v1/v2

v1 = velocity of light in first medium

v2 = velocity of light in second medium

3. Absolute Refractive index

n = c/v

c= velocity of light in air

v = velocity of light in given medium

4. Lateral Shift  5. Normal shift on a single surface

Normal shift Ns= t[1-1/n]

6. Relation between refractive index and critical angle

n = 1/sin C

7. Refraction through a prism Refractive index of the prism n = [sin(A+δ/2)]/sin A/2

8. Deviation produced by a thin film

d = (n-1) A

(n-1) is called the refractivity of the material

9. Angular dispersion between two colours

Angular dispersion = (nv-nr)A

nv, nr is the refractive index of violet light and red light

10. Dispersive power

ω = nv– nr/n-1

11. Lens makers formula for thin lenses

1/f = (n-1) { 1/R1 – 1/R2}

12. Power of lens

P = 1/f

13. Equivalent focal length of combination of two thin lenses

1/f = 1/f1 + 1/f2