In This Topic we would study
- Concave, Convex, Plane Mirrors.
- Image formation.
- Frequently asked question of previous exams.
Some basic terms
Incident ray- A light ray which strikes to surface.
Angle of incidence- The angle between light of incident and Norman.
Reflected ray- Reflected incident ray from surface is called reflected ray.
Angle of reflection- Angle between reflected ray and Norman.
Normal- A perpendicular hypothetical line from surface.
Point of incidence– A particular point of surface where incident ray, reflected ray and norman have connected.
Some important formulas
1- R = 2F F = ½ R
2- Mirror formula- 1/v + 1/u = 1/f
3- Magnification of mirror = I/o = -v/u
4- Total no. of image between two mirror = 360/angle – 1
Types of Mirrors
1. Plane mirror
2. Spherical mirror
A- Convex mirror
B- Concave mirror
Pole – center point between reflector side of mirror.
Center of curvature-Mirror made by a sphere so the center of sphere is called Center of curvature.
Radius of curvature- Distance between pole and center of curvature.
Principle axis- a direct line connected to pole and center of curvature.
Real Image – Front of mirror
Virtual Image – Back side of mirror
Image formation in concave mirror
Formation of image depend on object position with respect to mirror.
Here is 6 position.
1- When object going near to mirror, Size of image will increase and going away from mirror.
2- In concave mirror image always real, when object position on focus point or before focus point.
1-when object on infinite
Note-when a ray passed from c it reflect back without change direction
- Image formed in focus point
- Real image
- Very small image
2- When object on between infinite and center of curvature.
- Image formed between focus and center of curvature
- Reverse smaller than object
3- When object on center of curvature.
- Image also formed in center of curvature
- Reverse and same size of object
4- When object on between centre of curvature and focus.
- Image formed away from center of curvature
- Bigger than object and reverse
5- When object on focus
- Reverse and very bigger than object
- Image formed on infinite
6- When object on between focus and pole.
- Image formed back side of mirror
- Bigger than object
Image formation in convex mirror
Two condition only
1- When object on infinite- image formed on focus, virtual, upright, smaller than object.
2- Anywhere before mirror- back side of mirror, virtual, upright, smaller than object.
Sign conversion for measurement of distance
- We using positive sign in direction of incident ray negative sign opposite of incident rays.
- Positive sign above principal axis and negative below p. axis.
- Focus distance of concave mirror is negative and positive of convex mirror.
Previous year questions
1- Mirror in front of driver seat would be
D- non of these
2- Mirror used by doctor for testing of ear, nose, mouth would be
A – convex
B – concave
C – plane
D – all above
3- Mirror used for shaving would be
A – Concave
B – Convex
C – Plane
D – A and B
4- Mirror for own face looking is
A – Concave
B – Convex
C – Plane
D – Both A and C
5- Image formed by a plane mirror
C – Both
D- Non of above
6- If two mirror placed on Angle of 45 then total number of image would be
Total no of image = 360/Angle – 1
7- For looking of full image of any object, size of mirror would be
A- Double of object
B- Half of object
C- Same as object
D- Triple of object
8- If two plane mirror place parallel to each other than the total no of image would be
9- Mirror using in lamp of street light is
D- Both A and B
Answers- 1.b, 2.b, 3.a, 4.c, 5.b, 6.b, 7.b, 8.d, 9.a
The rules of image formation in lenses are same as mirror but rules would be interchanged as following –
Rules of Concave Mirror = Rules of Convex Lenses
Rules of Convex Mirror = Rules of Concave Lenses
For any questions, write in comment box.
Best of Luck