If sunlight is focused on a paper using a con | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) The shortest time to burn the paper occurs when the sunlight is focused exactly at the focal point of the lens. Therefore, the focal length $f = 3

Vedclass · Accepted Answer

$20$

Vedclass · Answer

(B) The shortest time to burn the paper occurs when the sunlight is focused exactly at the focal point of the lens. Therefore, the focal length $f = 30 	ext{ cm}$.Using the lens maker's formula: $\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} ight)$.For a symmetric double convex lens, $R_1 = R = 60 	ext{ cm}$ and $R_2 = -R = -60 	ext{ cm}$.Substituting these values: $\frac{1}{30} = (\mu - 1) \left( \frac{1}{60} - \frac{1}{-60} ight)$.$\frac{1}{30} = (\mu - 1) \left( \frac{1}{60} + \frac{1}{60} ight) = (\mu - 1) \left( \frac{2}{60} ight) = (\mu - 1) \left( \frac{1}{30} ight)$.This implies $\mu - 1 = 1$, so $\mu = 2$.Given $\mu = \frac{\alpha}{10}$, we have $2 = \frac{\alpha}{10}$, which gives $\alpha = 20$.

Similar Questions

$A$ convex lens made of glass (refractive index $= 1.5$) has a focal length of $24 \ cm$ in air. When it is totally immersed in water (refractive index $= 1.33$),its focal length changes to: (in $cm$)

$A$ convex lens of focal length $f$ produces an image $\frac{1}{n}$ times the size of the object. The distance of the object from the lens is:

$A$ thin lens made of glass of refractive index $1.5$ has a front surface $+ 11 D$ power and back surface $-6 D.$ If this lens is submerged in a liquid of refractive index $1.6,$ the resulting power of the lens is

An achromatic telescope objective is to be made by combining the lenses of flint and crown glasses. This proper choice is

Vedclass Test Series

Exam Paper Generator

Online Exam Module