In natural convection heat transfer, the parameter is the
choose the right answer
a) nusselt number
b) rayleigh number
c) grashof number
d) lewis number

correct option is c

Explanation:

The Grashof number is a dimensionless number, which is named after renowned scientist  Franz Grashof. The Grashof quantity is defined as the proportion of the buoyant force to viscous force performing on a fluid in a pace boundary layer.

Its function in natural convection is more or less the same as that of Reynolds's number in compelled convection.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.