A thin lens has power of 10 dioptres which lens is it

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Answer

Hint: We have to find the change in power. For solving this question we have to know the focal length which is $p = \dfrac{1}{f}$ so when a lens is immersed in water then the focal length increased and we know that focal length is inversely proportional to the angular magnification so that the lens immersed in water that decreases the power. The power of lens is the reciprocal of its focal length. And then change the power of refractive index of lens material. Also, we have to find when it is placed in air. So, substituting all these values we will get the required answer.

Complete step by step answer:

Hence, the correct option is D. Which is required answer.

Note: Since, we know that when a lens is dipped in water its automatically focal length increases. Lens is a thin curved piece of glass. For solving focal length is also defined as it is the distance between the lens and the image sensor when the subject is usually used. Refractive index can be defined as the distance from a focal point of the lens or mirror to the corresponding plane.

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Text Solution

Solution : Here, the focal length of the lens is given in 'centimeters' so to calculate the power of this lens, we should first convert the focal length into 'meters' because our formula uses the focal length in 'meters'. <br> Now, 10 cm`=10/100`m ltbrge`0.1`m <br> So, Focal length, f`=0.1`m (A convex lens has positive focal length) <br> Now, putting this value of focal length in the formula for the power of a lens. <br> `P=1/(f"in metres")` <br> We get, `P=1/0.1` <br> or `P=(1 xx 10)/(1)` <br> Thus, Power, P=`+10` dioptres (or `+10`D) <br> Thus, the powerof this convex lens is `+10` dioptres which is also written as `+10`D. The plus sign with the power indicates that it is converging lens or convex lens.