Answer:
There are three basic categories of musical instruments: percussion, wind, and stringed instruments. Most musical instruments use resonance to amplify sound waves and make sounds louder. In a musical instrument, the whole instrument and the air inside it may vibrate when the head of the drum is struck.
Answer:

Explanation:
The Hi line of the Balmer series is emitted in the transition from n = 3 to n = 2 i.e.
and 
The wavelength of Hi line of the Balmer series is given by :




So, the wavelength for this line is 550 nm. Hence, this is the required solution.
Answer:
1. Wave period = 0.962 s
2. Will absorb red and blue and reflect green
Explanation:
1.
The wave period is:

Wavelength is the distance between crests. So replacing the given information:

2. In simple words the color of an object is the light it reflects. A green object reflects green light, and the rest is absorbed (red and blue).
Answer:
And the force of ( Attraction or repulsion) between the poles A and D ( maximum or minimum)