Answer : The change in momentum of an object is equal to the impulse that acts on it.
Explanation :
Change in momentum : The change in momentum of an object is the product of the mass and the change in velocity of an object.
The formula of change in momentum is,

Impulse : An impulse of an object is the product of the force applied on an object and the change in time. Impulse is also equivalent to the change in momentum of an object.

Proof :

Hence, the change in momentum of an object is equal to the impulse that acts on it.
In refraction, when a wave travels from one medium to another it changes speed.
Correct option is A.
Answer:
distance between object and image = 18.9 cm
Explanation:
given data
radius of curvature = 18 cm
focal length = 1/2 radius of curvature
magnification = 40%
to find out
distance between object and image
solution
we know lens formula that is
1/f = 1/v + 1/u ....................1
here f = 18 /2 and v and u is object and image distance
and we know m = 40% = 0.40
so 0.40 = -v / u
so here v = - 0.40 u
so from equation 1
1/f = 1/v + 1/u
2/18 = - 1/0.40u + 1/u
u = -13.5 cm ..................2
and
v = -0.40 (- 13.5)
v = 5.4 cm ......................3
so from equation 2 and 3
distance between object and image = 5.4 + 13.5
distance between object and image = 18.9 cm
The heat capacity and the specific heat