Question

An object located 32cm in front of a lens forms an image on a screen 8 cm behind the

lens:

(a)find the focal length of the lens

(b) determine the magnification

(c) what is the nature of the lens

(d) draw the ray diagram to show the formation of the image in this case​

Answer 1

a. When an object falls freely to the ground, it is under the effect of a constant force known as force of gravity. No other forces act on it. Hence, from Newton's second law of motion, we can say that this constant force of gravity accelerates the the freely opposite, their effects do not get cancelled because these action and reaction forces do not act on the body. ball has s ball than a cricket ball moving with the same velocity.

b. Even though the magnitudes of action force and reaction force are equal and their directions are opposite, their effects do not get

cancelled.

c. It is easier to stop a tennis ball as compared to a cricket ball, when

both are travelling with the same velocity.

d. The velocity of an object at rest is considered to be uniform...

Answer 2

Let A be the plate area and d be the distance between the plates,

1) A dielectric slab of thickness t is inserted,

Due to polarization inside the dielectric electric field will reduce,

So outside of dielectric, field = E₀

inside of dielectric, field = E = E₀/k

where k is the dielectric constant,

So the net potential will be,

V = Et + E₀(d-t)

=> V = E₀t/k + E₀(d-t)

=> V = E₀(d - t + t/k)

we know that, E₀ = q/ε₀A

=> V = q(d - t + t/k)/ε₀A

=> C = q/V

=> C = ε₀A/(d - t + t/k)

which is the required expression for capacitance,

2) A metallic plate of thickness t is inserted,

when a conducting metallic plate is inserted then electric field inside the plate will be zero

=> E = E₀/k = 0

=> k = ∞

hence putting the value of k in the above equation we get,

C = ε₀A/(d - t)

which is the required expression for capacitance with a metallic plate.

Thank you. Hope it helps