Why can’t cells be seen with the naked eye?

The majority of the cells cannot be seen directly with our naked eyes because cells have extremely small eyes which are beyond the human eye vision. Microscopes are composed of the combination of lenses which forms a magnified image.

give me abc and i will get it for u.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.