$Lux$ is equal to:

$A$ lamp is hanging at a height of $4\,m$ above a table. The lamp is lowered by $1\,m$. The percentage increase in illuminance will be.....$\%$

In a movie hall,the distance between the projector and the screen is increased by $1\%$. The illumination on the screen is:

When sunlight falls normally on Earth,a luminous flux density (illuminance) of $1.57 \times 10^5 \; lm/m^2$ is produced on Earth. The distance of Earth from the Sun is $1.5 \times 10^8 \; km$. The luminous intensity of the Sun in candela is:

Which of the following is correct regarding microscope and telescope?

$A$ concave mirror is placed on a horizontal table with its axis directed vertically upwards. Let $O$ be the pole of the mirror and $C$ its centre of curvature. $A$ point object is placed at $C$. It has a real image,also located at $C$. If the mirror is now filled with water,the image will be