Question

Hola Brainlians !!!

Read the passage given in the attachment and answer the following questions

1) Focal length of a concave lens 20cm. What is it's power.

2) What lessons of life do you learn from the relation
P = P1 + P2

Class - 10th
Chapter - Light, Reflection and Refraction

• Kindly don't spam
• Kindly don't copy answers from web
• Quality Answer needed
• ​

Answer 1

$\sf{\huge{\underline{\green{Answer\:1:-}}}}$

The focal length of a concave lens 20 cm.

f = 20 cm

The power is defined as the ability of the lens to converge the ray of light falling on it.

We know,

Power of lens is = $\dfrac{1}{focal\:length}$

• SI of power is dioptre.

• SI of focal length is meter .

P = $\dfrac{1}{f}$

f = 20 cm = $\dfrac{20}{100}$ =

➝ P = $\dfrac{1}{20/100}$

➝ P = $\cancel{\dfrac{100}{20}}$

➝ P = 5 dioptre

$\sf{\huge{\underline{\green{Answer\:2:-}}}}$

The power of the unification of one or more lenses being in correspondence are equals to the algebraic sum of the power of a independent lens.

P = P1 + P2 + P3 + ...

Powers must be taken in proper sign .

• Convex stands for + ve .

• Concave stands for - ve .

If it is seperated by distance d meter

P = P1 + P2 - d1 (P1.P2)

______________________________________

Answer 2

Explanation:

1)given:

f = 20cm

To find:

p=?

$p = 1 / f$

p = 1/20 [ f should be in metre]

P= 1/0.2m

p =5D

therefore p = 5D

2)The relationship for Boyle's Law can be expressed as follows:

P1V1 = P2V2

[where P1 and V1 are the initial pressure and volume values]

[ P2 and V2 are the values of the pressure and volume of the gas after change.]

we can see this in industries, isothermal process, wherein temperature of gas remains constant.

(or)

= P1 + P2 + P3 + ...

Powers must be taken in proper sign .

Convex stands for + ve .

Concave stands for - ve .

If it is seperated by distance d meter

P = P1 + P2 - d1 (P1.P2)

hope it is helpful

!own answer!