No matter how far you stand from a mirror,your image appears erect. The mirror is likely to be

Where should an object be placed in front of a convex lens to get a real image of the size of the object?

The refractive index of diamond is $2.42$. What is the meaning of this statement?

Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

An object is placed at a distance of $10\, cm$ from a convex mirror of focal length $15\, cm$. Find the position and nature of the image.

$A$ 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.