This document provides an overview of optics and ray optics taught by Jayant Nagda. It includes definitions of key terms like luminous objects, non-luminous objects, reflection, laws of reflection, and plane mirrors. Plane mirrors are discussed in detail, including how they produce virtual, upright images that are laterally inverted compared to the object. The document also distinguishes between real and virtual objects/images and different types of images. Live classes are offered for JEE preparation in classes 11 and 12 on the Unacademy subscription platform.

1. 12
CLASS
Jayant Nagda
Ray Optics
Laws of Reflection

2. B.Tech, IIT Bombay
Jayant Nagda
IIT-JEE AIR - 161
12+ Years of Teaching Experience
Trained Million+ students
Best Content Award

3. Corpuscular theory Light is made of tiny particles called corpuscles
which travel in a straight line
Light behaves as a wave as well as particle.
What is Light ?

4. Ray Optics
or
Geometrical Optics
Wave Optics
or
Physical Optics
Optics Study of Light & its Properties

5. Considering rectilinear motion of light.
Geometrical Optics
Casts Shadows
Newton’s Opticks: light as stream of particles
Explains: Reflection, Refraction, Image formation
Doesn’t Explain: Diffraction/ Interference
Based on
Optics

6. Considering phenomenon which explain wave nature of light.
● Diffraction: bending of wave around obstacles
● Interference: light + light = dark
● Polarisation
Wave Optics
Optics

7. Rectilinear Propagation of Light
Light travels in a straight line in a homogeneous isotropic medium
(Except when light enters a new medium if deflects)
Understanding Light

8. Light ray cannot be seen as it moves through space unless
it is scattered / reflected by an obstacle.
❏ Light is Invisible
Understanding Light

9. In every case light from source enters our eyes where an image is
made and our brain is able to make out those signals.
❏ How we see things around us ?
Understanding Light

10. Luminous Objects Objects which generate their own light
Types of Objects

11. Objects which are capable of reflecting light
Non luminous / Illuminated Objects
Types of Objects

12. The phenomenon of turning back of light, when incident on
the boundary of two media, is called Reflection.
Plane Mirror
Surfaces which cause reflection are called Reflectors or Mirror.
Mirror :- polished glass with silvering on one side.
Reflection of Light

13. Representation of a light ray
Beam/Bundle of light ray
Pencil of light ray
Motion of a Light Ray

14. Plane Mirror
Light ray falling on the mirror.
Incident Ray
Light ray going away from mirror.
Reflected Ray
Reflection of Light

15. Plane Mirror
Reflected Ray
Incident Ray Normal
i r
1. Angle of Incidence is equal
to Angle of Reflection
∠ i = ∠ r
O : Point of incidence
AO : Incident ray
ON : Normal
i : Angle of Incidence
r : Angle of Reflection
A
B
O
N
Reflection of Light

16. 2. Incident ray, Normal to the mirror and Reflected ray,
all lie in the same plane.
1. Angle of Incidence is equal to Angle of Reflection
∠ i = ∠ r
Plane Mirror
Reflected Ray
Incident Ray Normal
i r
A
B
O
N
O : Point of incidence
AO : Incident ray
ON : Normal
i : Angle of Incidence
r : Angle of Reflection
Laws of Reflection

17. Angle between the light incident on an optical instrument
and final emergent ray.
angle through which incident light gets turned through due to
reflection.
30o
Example:
Angle of Deviation ઠ

18. 450
N
O
Determine angle of deviation ઠ of incident ray

19. angle of deviation
450
450
N
O
900 Anti clockwise
δ = 900
Determine angle of deviation ઠ of incident ray

20. N
O
Determine angle of deviation ઠ of light ray incident at an angle θ with
normal
θ
A. θ Clockwise
B. θ Anticlockwise
C. π - θ Anticlockwise
D. π - 2θ Anticlockwise

21. Draw the reflected ray and determine the
angle of deviation for each case of final emergent ray
O
200
1.
A. 20o
B. 40o
C. 60o
D. 80o

22. Draw the reflected ray and determine the
angle of deviation for each case of final emergent ray
300
2.
Horizontal ray
A. 20o
B. 40o
C. 60o
D. 80o

23. Light is incident on the plane mirror as shown.
If incident ray is rotated through an angle ‘θ’ anticlockwise,
what is the angle by which reflected ray turns through,
keeping mirror steady at all times.
A. θ Clockwise
B. θ Anticlockwise
C. 2θ Clockwise
D. 2θ Anticlockwise

24. If incident ray is steady but mirror turns through by ‘θ’
clockwise, by what angle is reflected ray turned through?
A. θ Clockwise
B. θ Anticlockwise
C. 2θ Clockwise
D. 2θ Anticlockwise

25. If incident ray is steady but mirror turns through by ‘θ’
clockwise, by what angle is reflected ray turned through?

26. if incident ray is steady but mirror turns through by ‘θ’
clockwise, by what angle is reflected ray turned through?

27. At what angle from horizontal must we keep the
mirror in order to get a vertical reflected ray
300
A. 15o
B. 30o
C. 45o
D. 60o

28. Normal Incidence
In case light is incident normally
Grazing Incidence
In case light strikes the reflecting
surface tangentially
Special Cases

29. 1. Consider any two light rays emanating (starting) from object.
2. Apply law of Reflection on each of them.
3. Find the meeting point / intersection of those reflected rays.
Tracing the Image

30. Image formation from Plane Mirror

31. ● I is virtual image,
● at same distance from
mirror as object.
● Same size as object
O I
Image formation from Plane Mirror

32. Object - Source of light rays incident on optical system
Object is real if two or more rays emanate (start)
or seem to emanate from a point.
Real Object
Diverging incident ray
Types of Objects

33. Virtual Object
A converging set of Incident rays
which did not appear to emanate from a point.
Real image I O
Virtual Object
Types of Objects

34. Real image
Image: A point where rays converge after
interaction with optical element.
Real image is formed when rays actually meet after
the interaction with optical element
Real image can be captured on a screen
Real O Real image
Convex lens
Converging Reflected Rays
Types of Image

35. Virtual image If rays, after interaction with optical element,
do not meet (converge) but appear to
emanate from a point, then a virtual image is formed
Real Object Virtual image
Diverging Reflected Rays
Types of Image

36. diverging Real Object
converging Virtual Object
converging Real Image
diverging Virtual Image
Incident rays
Reflected rays
Types of Objects & Images

37. Image formation from Plane Mirror

38. Image formation from Plane Mirror
B
A
C
Mirror
Object

39. ● I is virtual image,
● at same distance from mirror as object.
● Same size as object
● Upright
● Left-Right reversal (lateral inversion)
D
E
B
A
C
mirror
h0
hi
θ
θ
θ
Object Image
Image formation from Plane Mirror

40. ● Left-Right reversal (lateral inversion)
Image formation from Plane Mirror
Right Hand
Left Hand on Image

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