Question

Our rooms become brighter in the day time although there is no direct sunlight in our room why

Answer 1

Solution:

The sun is intensely bright.

Hence, even the smallest amount of reflective sunlight is so powerful that it lights up great surface area.

When proper ventilation is done in the rooms and when the sunlight hits the surface of walls and floors it reflects back thereby lighting up the entire room.

Answer 2

Even without direct sunlight entering a room, the room brightens up because of the phenomenon called the scattering of light or the Rayleigh scattering.

While reflection and refraction have indicated that light travels in a straight line, but because the photons of the light are travelling at different intensity, they tend to scatter.

It is these stray photons that illuminates the room.