D. similar types of rocks and fossils
Answer:
(a) 47.08°
(b) 47.50°
Explanation:
Angle of incidence = 78.9°
<u>For blue light :
</u>
Using Snell's law as:
Where,
Θ₁ is the angle of incidence
Θ₂ is the angle of refraction
n₂ is the refractive index for blue light which is 1.340
n₁ is the refractive index of air which is 1
So,
Angle of refraction for blue light = sin⁻¹ 0.7323 = 47.08°.
<u>For red light :
</u>
Using Snell's law as:
Where,
Θ₁ is the angle of incidence
Θ₂ is the angle of refraction
n₂ is the refractive index for red light which is 1.331
n₁ is the refractive index of air which is 1
So,
Angle of refraction for red light = sin⁻¹ 0.7373 = 47.50°.
Explanation:
We have,
Surface area, 
The current varies wrt time t as :

(a) At t = 2 seconds, electrical charge is given by :

(b) Current is given by :

Instantaneous current at t = 1 s is,

(c) Current is, 
Current density is given by electric current per unit area.

Therefore, it is the required explanation.
Question 1's answer is, if we change the length of the string allowed to vibrate, then the frequency (and pitch) of the string vibration will change. This is because the tension of the string determines the pitch.
Question 2's answer is 2. This can be solved by doing simple division. 30/15 = 2.
Question 3's answer is short bars. Each bar on a xylophone produces a different pitch; the shorter the bar, the higher the pitch.
Hope this helps.