Question

in a combination of lenses in contact the power of the first lenes is +2.5 D and the focal length of the second lens is -25 cm.Calculate the power of the lens combination?


No spamming please

class 12 th optics

​

Answer 1

Answer:

hey here is your answer

pls mark it as brainliest

Explanation:

$to \: find = \\ power \: of \: lens \: combination \\ \\ given = \\ for \: a \: convex \: lens \\ power \: (P1) = + 2.5 \: D \\ \\ for \: a \: concave \: lens \\ focal \: length \: (f) = - 25.cm = - 0.25 \: m \\ let \: its \: power \: be \: \: P2$

$so \: we \: know \: that \\ power \: (P) = \frac{1}{f \: (m)} \\ \\ so \: for \: concave \: lens \\ \\ P = \frac{1}{ - 0.25} \\ \\ P2 = - 4 \: D \\ \\ hence \: applying \: \\ power \: of \: combination \: (P) = P1 + P2 \\ = 2.5 \: + \: ( - 4) \\ = 2.5 - 4 \\ = - 1.5 \: D$

$since \: one \: of \: the \: lens \: is \: concave \\ the \: other \: will \: also \: act \: as \: concave \: only \\ \\ thus \: power \: of \: their \: lens \: combination \: (P) \: \\ is \: - 1.5 \: D$

Answer 2

Answer:

100

Explanation:

Power one of lens = P1 = +3.5D (Given)

Power two of lens = P2 = -2.5D (Given)

Power combination = P1 + P2

Thus,

Power of combination = +3.5 D +(-2.5 D )

= 3.5 D -2.5 D

= 1 D

Power = 1/focal length(m)

1 = 1/f

f = 1/1

f = 1 metre

Thus, the f of combination = 1×100 = 100 cm

Therefore, if two thin lenses of power +3.5D and -2.5D are placed in contact then the power and focal length of the lens combination will be 100m.

You rated our customer service as good.