Can a plane mirror be called a spherical mirror?

What is meant by power of a lens? Define its $SI$ unit. You have two lenses $A$ and $B$ of focal lengths $+10\, cm$ and $-10\, cm$ respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed $8\, cm$ from the lens? Draw a ray diagram to justify your answer.

$A$ full-length image of a distant tall building can definitely be seen by using:

Give one use of a concave lens.

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

Define the term reflection.