Question

hello

answer these above Q , please :)​

Answer 1

Answer:

Explanation:

To measure the focal length of a converging (convex) lens. To measure the focal length of a converging (convex) lens. Using the formula: 1/u + 1/v = 1/f, the focal length f of the lens can be found.

Answer 2

Answer (20) :-

→ Time (t) = 1 second.

Option (1) is correct.

Step - by- step explanation:-

Given that :-

$\implies \: dq \: = 4 \: calories \\ \\ \implies \: dt \: = 4 \: minutes$

Solution :-

We know that,

$\frac{dq}{dt} = \frac{ak}{2x} (t2 - t1) \\ \\ \implies \: \frac{ak}{2x} (t2 - t1) = \frac{20}{4} \\ \\ \implies \: \frac{ak}{2x} (t2 - t1) = 5 \\ \\ \implies \: \frac{ak}{x} (t2 - t1) = 10 \: ............(1)$

Now ,

When they are one above the other,

$\frac{dq}{dt} = \frac{2ak}{x} (t2 - t1) \: = \frac{20}{t}$

$\implies \: 2 \times \bigg( \frac{ak}{x} (t2 - t1) \bigg) = \frac{20}{t}$

Now from equation (1)

$\implies \: 2 \times 10 = \frac{20}{t} \\ \\ \implies \: 20t = 20 \\ \\ \implies \: \boxed{t = 1 \: second}$