Because dark line spectra result from passing white light through ionized gasses and plasmas, which is what the atmosphere of stars are made of. These frequencies are scattered by the star's atmosphere as it leaves the surface (photosphere) of the star, and don't make it to earth.
Answer:
Explanation:
Since the wires attract each other , the direction of current will be same in both the wires .
Let I be current in wire which is along x - axis
force of attraction per unit length between the two current carrying wire is given by
x 
where I₁ and I₂ are currents in the wires and d is distance between the two
Putting the given values
285 x 10⁻⁶ = 10⁻⁷ x 
I₂ = 16.76 A
Current in the wire along x axis is 16.76 A
To find point where magnetic field is zero due the these wires
The point will lie between the two wires as current is in the same direction.
Let at y = y , the neutral point lies
k 2 x
= k 2 x 
25.5y = 16.76 x .3 - 16.76y
42.26 y = 5.028
y = .119
= .12 m
Because they occur at an atomic level, changing the actual structure of the thing.
Hope it helps
9*
m
Explanation:
Step 1:
We are given the initial length of the Pyrex glass dish at a particular temperature and need to calculate the change in the length when the temperature changes by 120° C. The coefficient of linear expansion of Pyrex is provided.
Step 2:
Change in length = Coefficient of linear expansion * Change in temperature * Initial length
Step 3:
Coefficient of linear expansion = 3*
/°C
Change in temperature = 120°C = 120 K
Initial length = 0.25 m
Step 4:
Change in length = 3*
* 120 * 0.25 = 9*
m