Question

power of lens is + 2.5 D what kind of lens it is and its focal length​

Answer 1

Answer:focal length =0.004cm

It is a convex lens.

Explanation:

P=1/f

P=+2.5D

2.5=1/f

f=1/2.5 m

f=1/250 cm

f=1/250×4/4 cm

f=4/1000 cm

Therefore, f=0.004 cm

Answer 2

Question :-

power of lens is + 2.5 D what kind of lens it is and its focal length ?

Answer :-

• convex lens
• focal length = 40 cm

Given :-

• Power of lens = +2.5 D

To find :-

• what kind of lens ?
• focal length = ?

Solution :-

• The power of this lens has positive sign , so it is a convex lens .

Now,

We all know that

• Power ( P) = 1/f (in metres )

So,

putting the values in the above formula we get,

➞ +2.5 = 1/f

➞ f = 1/2.5 m

Now convert the 2.5 m in cm we get ,

➞ f = 1/2.5 × 100 cm

➞ f = 40 cm

So, Focal length ( f ) = 40 cm or ( + 40 cm )

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