<span>This is because Helium
has two valence electrons compared to Hydrogen which has only one. Helium has
more energy levels for an electron to jump thus more spectral lines to occur.
The spectral lines relating to each change of energy level would be more
grouped together and hence the greater chance of them falling in the visible
range.</span>
No, it will only melt if the temperature is lowered. If you compress it, it will change the shape, but it will not change the state it is in (i.e. solid).
Answer:
The air resistance on the skydiver is 68.6 N
Explanation:
When the skydiver is falling down, there are two forces acting on him:
- The force of gravity, of magnitude
, in the downward direction (where m is the mass of the skydiver and g is the acceleration due to gravity)
- The air resistance,
, in the upward direction
So the net force on the skydiver is:

where
m = 7.0 kg is the mass

According to Newton's second law of motion, the net force on a body is equal to the product between its mass and its acceleration (a):

In this problem, however, the skydiver is moving with constant velocity, so his acceleration is zero:

Therefore the net force is zero:

And so, we have:

And so we can find the magnitude of the air resistance, which is equal to the force of gravity:

B.) The retina is the layer containing t<span>he light sensing nerve cells (rods and cones)
The lens helps the eye focus light on the retina, the cornea is the outer transparent structure that covers the iris and helps the eye focus, and the pupil is the opening through which light enters the eye.</span>