<span>C is the correct answer. Electron microscopes require a vacuum to work, so living cells cannot be seen because they cannot respire. Light microscopes use a ray of visible light instead of a beam of electrons to magnify something so it can be seen by the naked eye. There are two different types of electron microscope: transmission (TEM) and scanning (SEM).</span>
Explanation:
Given that,
Force, 
Position of the particle, 
(a) The toque on a particle about the origin is given by :
Taking the cross product of above two vectors, we get the value of torque as :
(b) Let 
is the angle between r and F. The angle between two vectors is given by :
Answer:
Explanation:
a )
In space due to weightlessness both astronaut and her oxygen tank will float .
when she throws the tank away from spacecraft , she will have a velocity in opposite direction ie towards the spacecraft . This happens due to conservation of momentum . She creates a momentum away so that she can get a momentum towards the spaceship.
So
m₁ v₁ = m₂v₂
12 x 8 = ( 87 - 12 ) x v₂
v₂ = 1.28 m /s
Time allowed = 2 x 60
= 120 s
So maximum distance upto which she can remain away from spacecraft
= 120 x 1.28
= 153 m .
b )
The Newton's law which explains the theory behind it is "third law of motion" . This law gives law of conservation of momentum .
answer
64 is C (c) 1-Bromo-3-methylbutane
63 is D
i is secondary ii is primary
