Answer
The image formed by a concave mirror will be virtual, erect and magnified when the object is placed only between the pole and the principal focus of the mirror.
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Answer:
Only electrons
Explanation:
When a current flows through a metal wire, the moving charges are electrons since electric current is the flow of electric charge in an electric circuit. This electric charge are therefore electrons.
Answer:
a
The focal length of the lens in water is 
b
The focal length of the mirror in water is 
Explanation:
From the question we are told that
The index of refraction of the lens material = 
The index of refraction of the medium surrounding the lens = 
The lens maker's formula is mathematically represented as
![\frac{1}{f} = (n -1) [\frac{1}{R_1} - \frac{1}{R_2} ]](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bf%7D%20%3D%20%28n%20-1%29%20%5B%5Cfrac%7B1%7D%7BR_1%7D%20-%20%5Cfrac%7B1%7D%7BR_2%7D%20%20%5D)
Where 
is the focal length
is the index of refraction
are the radius of curvature of sphere 1 and 2 of the lens
From the question When the lens in air we have
![\frac{1}{f_{air}} = (n-1) [\frac{1}{R_1} - \frac{1}{R_2} ]](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bf_%7Bair%7D%7D%20%3D%20%28n-1%29%20%5B%5Cfrac%7B1%7D%7BR_1%7D%20-%20%5Cfrac%7B1%7D%7BR_2%7D%20%20%5D)
When immersed in liquid the formula becomes
![\frac{1}{f_{water}} = [\frac{n_2}{n_1} - 1 ] [\frac{1}{R_1} - \frac{1}{R_2} ]](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bf_%7Bwater%7D%7D%20%3D%20%5B%5Cfrac%7Bn_2%7D%7Bn_1%7D%20-%201%20%5D%20%5B%5Cfrac%7B1%7D%7BR_1%7D%20-%20%5Cfrac%7B1%7D%7BR_2%7D%20%20%5D)
The ratio of the focal length of the the two medium is mathematically evaluated as
![\frac{f_water}{f_{air}} = \frac{n_2 -1}{[\frac{n_2}{n_1} - 1] }](https://tex.z-dn.net/?f=%5Cfrac%7Bf_water%7D%7Bf_%7Bair%7D%7D%20%3D%20%5Cfrac%7Bn_2%20-1%7D%7B%5B%5Cfrac%7Bn_2%7D%7Bn_1%7D%20-%201%5D%20%7D)
From the question
= 79.0 cm
and the refractive index of water(material surrounding the lens) has a constant value of 
b
The focal length of a mirror is dependent on the concept of reflection which is not affected by medium around it.
(89000/102000)×100
=87.25%
(92000/104000)×100
=88.46%
efficiency is (output/input)×100
if u get confused which way input and output should go, remember the smaller value is always output and it's above in the fraction, then only it's possible to get a efficiency lower than 100.
Answer:
v = 11 m/s is her final speed
Explanation:
work done by gravity = m g Δh = 40×9.8×10 = 3920 Joules
Work done by friction = - force×distance = - 20×100 = - 2000 Joules
[minus sign because friction force is opposite to the direction of motion]
Initial K.E. = (1/2) m u^2 = (1/2) × 40 × 5^2 = 500 Joules
Now, by work energy theorem
Work done = change in kinetic energy.
Final K.E. = initial K.E. + total work = 500 + 3920 - 2000 = 2420 Joules
Now, Final K.E. = (1/2) m v^2 [final speed being v= speed at the bottom]
⇒ 2420 = (1/2)×40×v^2
⇒ 121 = v^ 2
v = 11 m/s is her final speed
