Key relationship
1/f = 1/d + 1/q; m = −q/d; positive f concave, positive q real in front.
Physics · Class 12
Spherical mirror images
Ray Optics & Optical Instruments
A concave mirror can give a real inverted image or a virtual upright image depending on object position. A convex mirror gives a reduced virtual image. The focal-position limit produces parallel reflected rays.
Open the interactive experiment →Spherical mirror images
குழி ஆடியின் பிம்பம் பொருளின் இடத்தைச் சாரும். குவி ஆடி சிறிய மெய்நிகர் பிம்பம் தரும்.
Key notes, relationships and model limits
Remember
A concave mirror can give a real inverted image or a virtual upright image depending on object position. A convex mirror gives a reduced virtual image. The focal-position limit produces parallel reflected rays.
Common trap
Do not divide by zero at the focus or label infinity as a screen position.
Model limits
Paraxial spherical mirror; real-object distance d is positive. This uses positive real-image distances, not the Cartesian signed-u convention. f=0 is invalid; d=f gives an image at infinity.
What you will learn
Connect object position, image distance and magnification.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
f=20 cm and d=60 cm gives q=30 cm and m=−0.5.
Why this matters
The model connects spherical mirror images with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
An object is at a concave mirror focus. Where is the image?
- At the centre
- At infinity
- At the pole
Read the explanation
The equation gives 1/q=0, so reflected paraxial rays are parallel.
Course connection: Class XII Chapter 9. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.