When light crosses the boundary between layers with different densities, the light is refracted. (A).
Question: How fast was the arrow moving before it joined the block?
Answer:
The arrow was moving at 15.9 m/s.
Explanation:
The law of conservation of energy says that the kinetic energy of the arrow must be converted into the potential energy of the block and arrow after it they join:
where 
is the mass of the arrow, 
is the mass of the block, 
of the change in height of the block after the collision, and 
is the velocity of the arrow before it hit the block.
Solving for the velocity , we get:
and we put in the numerical values
,
and simplify to get:
The arrow was moving at 15.9 m/s
<span>Frequency of a sound wave is called the pitch. Higher frequencies have a higher pitch and lower frequencies have the opposite. When an ambulance travels by a listener, the frequencies are oscillating rapidly and causing the shrill, loud sounds that emanate from the sirens.</span>
Explanation:
A wave is a disturbance in a medium. For example, when some pebbles are thrown in water, the water particles gets disturbed. A wave is characterized by the following parameters i.e.
Frequency
Wavelength etc
The number of oscillations or vibrations in a medium is called the frequency of a wave.
Also, the distance between two consecutive crests and troughs is called the wavelength of a wave. The relationship between the wavelength and the frequency of a wave is given by :
Speed of wave = frequency × wavelength
