^Divergent power
^Divergent power
1. Bends the reflected (or refracted) rays away from the principal axis
2. Has negative optical power
3. e.g. a convex mirror & a concave lens (placed in rarer surroundings)
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^Convergent power
^Convergent power
1. Bends the reflected (or refracted) rays towards the principal axis
2. Has positive optical power
3. e.g. a concave mirror & a convex lens (placed in rarer surroundings)
4. our eyes
5. Used in compound microscope, telescopes, cameras.
^Magnified image
^Magnified image
- I > O
- v > u
- m > 1
Inequality sign reverses for diminished image
^Virtual focus
^Virtual focus
- A position on the principal axis where two or more reflected (or refracted) rays appears to meet
- situated infront of mirror
- g. focus of a convex mirror & that of a concave lens (placed in rarer surroundings)
^Real focus
^Real focus
- A position on the principal axis where two or more reflected (or refracted) rays actually meet
- situated infront of mirror
- g. focus of a concave mirror & that of a convex lens (placed in rarer surroundings)
^Virtual image
^Virtual image
- A position where two or more reflected (or refracted) rays appears to meet
- situated behind the mirror & behind the object on same side of lens
- v = + ve for mirrors & – ve for lenses.
- Can’t be obtained on screen, without using a convergent system.
^Real image
^Real image
- A position where two or more reflected (or refracted) rays actually meet
- situated infront of the mirror & behind the lens
- v = -ve for mirrors & +ve for lenses.
- Can be obtained on screen
^Virtual object
^Virtual object
1. A position at which incident rays converge
2. situated behind the mirror i.e. towards the polished side
3. u = + ve for both lenses & mirror
^Real object
^Real object
1. A position from which incident rays diverge
2. situated infront of mirror i.e. towards the reflecting side
3. u = – ve for both lenses & mirror
4. Unless mention assume object to be real, transverse, producing paraxial rays.
^Convex mirror & Concave lens
^Convex mirror & Concave lens
A convex mirror has Inner or depressed side polished. A concave lens is thick near edges & thin near the center. They have following common features
- Virtual focus
- Diverge light rays striking on them
- Negative optical power
- Can form only a diminished & virtual image of a real object.
