Answer:
d. It increases numerical aperture and maintains a uniform light speed.
Explanation:
In optical microscopes, various immersion mediums are used to improve or enhance the resolution. Immersion oils like cedar and Leica oils are one of those mediums which are used to improve resolution by increasing the numerical aperture and keeping the speed of light uniform.
I think it is electron. Electrons are located outside of the nucleus
In a block and tackle, some friction in the pulleys will reduce the mechanical advantage of the machine. To include friction in a calculation of the mechanical advantage of a block and tackle, divide the weight of the object being lifted by the weight necessary to lift it.
Hope this helps
<h2>
Answer: 13.61 N/m</h2>
Hooke's law establishes that the elongation of a spring is directly proportional to the modulus of the force 
applied to it, <u>as long as the spring is not permanently deformed</u>:
(1)
Where:
is the elastic constant of the spring. The higher its value, the more work it will cost to stretch the spring.
is the length of the spring without applying force.
is the length of the spring with the force applied.
According to this, we have a spring where only the force due gravity is applied.
In other words, the force applied is the weigth 
of the block:
(2)
Where 
is the mass of the block and 
is the gravity acceleration.
(3)
(4)
Knowing the force applied and 
and 
, we can substitute the values in equation (1) and find :
(5)
(6)
<u>Finally:</u>
Check the 1st 2nd 3rd and 4th boxes
