Answer:
a

b

c

Explanation:
From the question we are told that
The frequency is 
The length of the vibrating string is 
The mass is 
Generally the wavelength is mathematically represented as

=> 
=> 
Generally the wave speed is

=> 
=> 
Generally the tension on the wire is mathematically represented as

=> 
=> 
Answer:
Concave Lens Uses. Telescope and Binoculars Spectacles Lasers Cameras FlashlightsPeepholes. ...
Used in telescope and binoculars. ...
Concave lens used in glasses. ...
Uses of concave lens in lasers. ...
Use of concave lens in cameras. ...
Used in flashlights. ...
Concave lens used in peepholes.