O lentila biconvexa simetrica din sticla, avand indicele de refractie n = 1,5, cu distanta focala f = 60 cm, formeaza imaginea unui obiect asezat la 90 cm de ea. Sa se precizeze unde se formeaza imaginea, natura acesteia, marirea liniara transversala. Sa se calculeze convergenta lentilei si raza acesteia.

answer; talc and gypsum;

the answer is a! (2.9 x 10^-18 j) hope i could someone. : )

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.