Answer: f=150cm in water and f=60cm in air.
Explanation: Focal length is a measurement of how strong light is converged or diverged by a system. To find the variable, it can be used the formula:
= (nglass - ni)(
-
).
nglass is the index of refraction of the glass;
ni is the index of refraction of the medium you want, water in this case;
R1 is the curvature through which light enters the lens;
R2 is the curvature of the surface which it exits the lens;
Substituting and calculating for water (nwater = 1.3):
= (1.5 - 1.3)(
-
)
= 0.2(
)
f =
= 150
For air (nair = 1):
= (1.5 - 1)(
-
)
f =
= 60
In water, the focal length of the lens is f = 150cm.
In air, f = 60cm.
When an object's atoms move faster, its thermal energy increases and the object becomes warmer.
Answer:
Terminal velocity of object = 12.58 m/s
Explanation:
We know that the terminal velocity is attained when drag force and gravitational force are of the same magnitude.
Gravitational force = mg = 80 * 9.8 = 784 N
Drag force = 
Equating both, we have

So v = 12.58 m/s or v = -15.58 m/s ( not possible)
So terminal velocity of object = 12.58 m/s
Answer:
R' = 4R
The resistance will become 4 times the initial value.
Explanation:
The resistance of a wire at room temperature, is given by the following formula:
R = ρL/A ----------- equation 1
where,
R = Resistance of wire
ρ = resistivity of the material
L = Length of wire
A = Cross-sectional area of wire
Now, if the length (L) is multiplied by 4, then resistance will become:
R' = ρ(4L)/A
R' = 4 (ρL/A)
using equation 1:
<u>R' = 4R</u>
<u>The resistance will become 4 times the initial value.</u>