It can be observed without changing the identity of the object.
<span>vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.</span>
<span>The answer to this question is that non metals are
volatile. Volatile means evaporating easily. Non metals have the
characteristics and properties of being brittle and poor conductors of heat and
electricity. Non metals are also good oxidizing agents and physically they may
be in liquid, solid or gas state. Examples of non metals are carbon, sulfur,
argon, neon, and hydrogen.</span>
Answer:
Explanation:
The energy of a photon is: 
when h is the Planck constant.
Then, we calculate the energy of a photon with a wavelength equal to 550 nm.
To find the number of photons we can use this equation:
Have a nice day!
