Answer:
4 times greater
Explanation:
<u>Step 1:</u> Calculate light-collecting area of a 20-meter telescope (A₁) by using area of a circle.
Area of circle = π*r² =
Where d is the diameter of the circle = 20-m


A₁ = 314.2 m²
<u>Step 2:</u> Calculate light-collecting area of a 10-meter Keck telescope (A₂)

Where d is the diameter of the circle = 10-m

A₂ = 78.55 m²
<u>Step 3</u>: divide A₁ by A₂

= 4
Therefor, the 20-meter telescope light-collecting area would be 4 times greater than that of the 10-meter Keck telescope.
The answer is 34 you have to add the numbers and divide them by how many numbers there are
Answer:
0.2cm towards the retina.
Explanation:
the focal length of the frog eye is
(1/f) = (1/10) + (1/0.8)
f = 0.74cm
Since the distance of the object is 15cm Hence
(1/0.74) = (1/15) + (1/V)
V = 0.78cm
Therefore the distance the retina is to move is
0.78cm - 0.8cm = 0.02cm towards the retina.
Answer:

Explanation:
Given that the temperature of
of water and
of water are
at
and
respectively.
Let
, 
and
,
.
The specific heat capacity of water is,
.
Let the final temperature of the mixture be
.
As there is no energy loss, so, the energy loss by the water at higher temperature, i.e.
, will be equal to the energy gain by the water at lower temperature, i.e.
.

[ both sides divided by
]



Now, putting the given value in the above equation, we have


Hence, the temperature of the mixture will be
.