Name the mirror that can give an erect and enlarged image of an object.

$A$ convex lens forms a real and inverted image of a needle at a distance of $50\, cm$ from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also,find the power of the lens.

Light enters from air to glass having refractive index $1.50$. What is the speed of light in the glass? The speed of light in vacuum is $3 \times 10^8 \, m \, s^{-1}$.

We wish to obtain an erect image of an object,using a concave mirror of focal length $15\, cm$. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

$A$ ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

Find the focal length of a lens of power $-2.0 \, D$. What type of lens is this?