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Basile [38]
2 years ago
15

Change. Wax melting is an example of a chemical reaction. True or false

Physics
2 answers:
faltersainse [42]2 years ago
6 0
I believe it is a physical change not chemical
Alekssandra [29.7K]2 years ago
4 0

Answer:

False, because here only physical properties are changing.

luv,

Aria❤

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Four rivers have the same volume of water flow over time but fall from the different heights to power hydroelectric dams. which
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Like charges repel and opposite charges attract.

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Titanium metal requires a photon with a minimum energy of 6.94×10−19J to emit electrons. If titanium is irradiated with light of
butalik [34]

Answer:

a) 1.59(10)^{-19} J

b) 2.34(10)^{12} electrons

Explanation:

The photoelectric effect consists of the emission of electrons (electric current) that occurs when light falls on a metal surface under certain conditions.  

If the light is a stream of photons and each of them has energy, this energy is able to pull an electron out of the crystalline lattice of the metal and communicate, in addition, a kinetic energy.  

<u>This is what Einstein proposed: </u>

Light behaves like a stream of particles called photons with an energy  E:

E=\frac{hc}{\lambda} (1)  

So, the energy E of the incident photon must be equal to the sum of the Work function \Phi of the metal and the kinetic energy K of the photoelectron:  

E=\Phi+K (2)  

Where \Phi=6.94(10)^{-19} J is the minimum amount of energy required to induce the photoemission of electrons from the surface of Titanium metal.

Knowing this, let's begin with the answers:

<h3 /><h3>a)  Maximum possible kinetic energy of the emitted electrons (K)</h3>

From (1) we can know the energy of one photon of 233 nm light:

E=\frac{hc}{\lambda}

Where:

h=6.63(10)^{-34}J.s is the Planck constant  

\lambda=233 (10)^{-9} m is the wavelength

c=3 (10)^{8} m/s is the speed of light

E=\frac{(6.63(10)^{-34}J.s)(3 (10)^{8} m/s)}{3 (10)^{8} m/s} (3)

E=8.53(10)^{-19} J (4) This is the energy of one 233 nm photon

Substituting (4) in (2):

8.53(10)^{-19} J=6.94(10)^{-19} J+K (5)  

Finding K:

K=1.59(10)^{-19} J (5)  This is the maximum possible kinetic energy of the emitted electrons

<h3>b) Maximum number of electrons that can be freed by a burst of light whose total energy is 2 \mu J=2(10)^{-6} J</h3>

Since one photon of 233 nm is able to free at most one electron from the Titanium metal, we can calculate the following relation:

\frac{E_{burst}}{E}

Where E_{burst}=2(10)^{-6} J is the energy of the burst of light

Hence:

\frac{E_{burst}}{E}=\frac{2(10)^{-6} J}{8.53(10)^{-19} J}=2.34(10)^{12} electrons This is the maximum number of electrons that can be freed by the burst of light.

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