linear magnification of a mirror is -v/u and in the lens, it is v/u. why is negative in the mirror and positive in the lens. explain in detail
Real Images
- Real Image is an image which can be projected onto a screen.
- Real images are always located in front of the mirror and behind the lens.
- Real images are always inverted and never upright.
- Concave lenses, Convex mirrors and plane mirrors always form virtual images and can never form real images.
Virtual Images
- Virtual Image is an image which cannot be projected onto a screen.
- Virtual images are always located in behind the mirror and in front of the lens.
- Virtual images are always upright and never inverted.
Linear magnification:
- Also known as lateral or transverse magnification is the ratio of image length to object length measured in planes that are perpendicular to the optical axis.
Magnified image for mirror:
- The image length in the formula of ‘m’ for mirror is taken as negative because, the image distances i.e ‘v’ are always negative for virtual images .
- As the magnified image from a mirror is a virtual image, ‘v’ is taken as negative and that is why the formula of ‘m’ for mirror becomes, -v/u.
Magnified image for lens:
- As the magnified image from the lens is real image, the image distance ‘v’ is taken positive and the formula of magnification ‘m’ becomes ‘v/u’.
- However, in certain cases which involve more than one lens, the object distance can be negative.