$A$ convex mirror is used to form the image of a real object. Then tick the wrong statement.

Rays from the Sun converge at a point $15 \, cm$ in front of a concave mirror. Where should an object be placed so that the size of its image is equal to the size of the object?

$(a)$ Water has a refractive index of $1.33$ and alcohol has a refractive index of $1.36$. Which of the two media is optically denser? Give a reason for your answer. Draw a ray diagram to show the path of a ray of light passing obliquely from water to alcohol.
$(b)$ The absolute refractive index of diamond is $2.42$ and the absolute refractive index of glass is $1.50$. Find the refractive index of diamond with respect to glass.

What is the radius of curvature of a plane mirror?

What is meant by the power of a lens? Give its $SI$ unit. When two or more lenses are placed in contact,what will be their combined power?

What is the focal length of a plane mirror?