If we use a 10cm converging lens instead of a 5cm converging lens, would the first point at which the image focuses (as you slide away from the lamp) be closer to or farther from the lamp than it was for the 5cm lens?

first point at which the image focuses will be closer

Explanation:

given data

converging lens = 10 cm

converging lens = 5 cm

lens = 5 cm

to find out

would the first point at which the image focuses be closer or farther

solution

we apply here lens formula that is

1/f = 1/u + 1/v   1

so here

v = f × u / u - f

so here for f = 10 cm  v will be

v = 10u / u-10      2

and

for f = 5 cm v will be

v = 5u / u-5       .     3

now if we compare equation 2 and 3 we can say that

v for f = 5 cm is greater than v for f = 10 cm

so here first point at which the image focuses will be closer