What is the expression for magnification of a lens?

How can you identify the three types of mirrors without touching them?

How will you identify a convex lens by touching it?

What is the effect on the wavelength of light when it travels from a rarer to a denser medium?

Can a plane mirror be called a spherical mirror?

Name the spherical mirror used as:
$(a)$ $1.$ Shaving mirror,
$2.$ Rear-view mirror in vehicles,
$3.$ Reflector in searchlights.
$(b)$ Write any three differences between a real and virtual image.