Use the Inverse square law, Intensity (I) of a light is inversely proportional to the square of the distance(d).
I=1/(d*d)
Let Intensity for lamp 1 is L1 distance be D1 so on, L2 D2 for Intensity for lamp 2 and its distance.
L1/L2=(D2*D2)/(D1*D1)
L1/15=(200*200)/(400*400)
L1=15*0.25
L1=3.75 <span>candela</span>
Answer:

Explanation:
As we know that volume of cylinder is

Where v=volume , h= height or thickness and r= radius
Here,

Putting these values in the previous equation , we get

Therefore thickness is 27.5 m
Answer:
Explanation:
From the given information:
The initial PE
= m×g×h
= 5 kg × 9.81 m/s² × 10 m
= 490.5 J
The change in Potential energy P.E of the box is:
ΔP.E = 
ΔP.E = 0 -
ΔP.E = 
If we take a look at conservation of total energy for determining the change in the internal energy of the box;


this can be re-written as:

Here, K.E = 0
Also, 70% goes into raising the internal energy for the box;
Thus,


ΔU = 343.35 J
Thus, the magnitude of the increase is = 343.35 J