Ray Optics

Front 1

Light

Back 1

Electromagnetic radiation belonging to the region of electromagnetic spectrum of wavelength of about 400 nm to 750 nm

Hint 1

400nm to 750nm

Front 2

Two properties of light

Back 2

1. Light travels with enormous speed (c=3×108 m/s)

2. Light travels in a straight line

Hint 2

Fast and straight

Front 3

Ray of light

Back 3

The path of light traveling from one point to another along a straight line joining them

Front 4

Beam of light

Back 4

A bundle of rays of light

Front 5

Angle of reflection

Back 5

Angle between reflected ray and the normal to the reflecting surface or mirror

Front 6

Angle of incidence

Back 6

Angle between the incident ray and the normal

Front 7

Laws of reflection

Back 7

1. Angle of reflection equals angle of incidence

2. Incident ray, reflected ray and the normal to the reflecting surface at the point of incidence lie in the same plane

Front 8

Pole

Back 8

Geometric centre of a spherical mirror

Front 9

Optical centre

Back 9

Geometric centre of a spherical lens

Front 10

Principal axis of a spherical mirror

Back 10

Line joining the pole and centre curvature

Front 11

Principal axis of a spherical lens

Back 11

Line joining the optical centre with its principal focus

Front 12

Cartesian sign convention

Back 12

1. All distances are measured from the pole of the mirror or optical centre of the lens

2. Distance measured in the same direction as the incident light are taken as positive

3. Those measured opposite to the direction of incident light are taken as negative

4. Heights measured upwards wrt x-axis and normal to principal axis are positive

5. Heights measured downwards are negative

Front 13

Focus(F)

Back 13

The point from which paraxial beam of light seem to converge(concave mirror) or diverge(convex mirror) from it

Front 14

Focal length (f)

Back 14

Distance between the focus and pole of the mirror.

f=R/2 ;where R=radius of curvature of the mirror

Front 15

Image

Back 15

If rays emanating from a point actually meet at another point after reflection and/or refraction, that point is called the image of the first point.

An image is thus a point-to-point correspondence with the object established through reflection and/or refraction.

Front 16

Real image

Back 16

Image formed by rays actually converging at a point

Front 17

Virtual image

Back 17

Image formed by rays which do not actually meet but appear to diverge from a point when produced backwards

Front 18

Image formation

Back 18

1. Incident ray parallel to principal axis = reflected ray goes through focus

2. Ray passing through centre of curvature (concave) /ray appearing to pass through centre of curvature (convex) = reflected ray retraces it's path

3. Ray passing through focus (concave) /ray appearing to pass through focus (convex) = reflected ray is parallel to principal axis

4. Incident ray at the pole = reflected ray follows law of reflection

Front 19

Mirror equation

Back 19

1/v + 1/u = 1/f

Front 20

Linear magnification

Back 20

Ratio of height of image(h') to height of object(h)

m= h'/h = v/u

Front 21

Refraction of light

Back 21

Change in the angle of incidence of light at the interface of two media

And, 0°<i<90° ; i = angle of incidence

Front 22

Snell's law of refraction

Back 22

sin i/sin r = n21 ; where n21 = constant and refractive index of the second medium wrt the first medium, it is independent of the angle of incidence

Front 23

Rarer to denser

Back 23

• n21 >1

• r<i

• refracted ray bends towards normal

Front 24

Denser to rarer

Back 24

• n21 < 1

• r>i

• refracted ray bends away from normal

Front 25

#NOTE

Back 25

n12 = 1/n21