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Blababa [14]
4 years ago
9

Light with a wavelength of 495 nm is falling on a surface and electrons with a maximum kinetic energy of 0.5 eV are ejected. Wha

t could you do to increase the maximum kinetic energy of electrons to 1.5 eV?
Physics
1 answer:
devlian [24]4 years ago
8 0

Answer:

To increase the maximum kinetic energy of electrons to 1.5 eV, it is necessary that ultraviolet radiation of 354 nm falls on the surface.

Explanation:

First, we have to calculate the work function of the element. The maximum kinetic energy as a function of the wavelength is given by:

K_{max}=\frac{hc}{\lambda}-W

Here h is the Planck's constant, c is the speed of light, \lambda is the wavelength of the light and W the work function of the element:

W=\frac{hc}{\lambda}-K_{max}\\W=\frac{(4.14*10^{-15}eV\cdot s)(3*10^8\frac{m}{s})}{495*10^{-9}m}-0.5eV\\W=2.01eV

Now, we calculate the wavelength for the new maximum kinetic energy:

W+K_{max}=\frac{hc}{\lambda}\\\lambda=\frac{hc}{W+K_{max}}\\\lambda=\frac{(4.14*10^{-15}eV\cdot s)(3*10^8\frac{m}{s})}{2.01eV+1.5eV}\\\lambda=3.54*10^{-7}m=354*10^{-9}m=354nm

This wavelength corresponds to ultraviolet radiation. So, to increase the maximum kinetic energy of electrons to 1.5 eV, it is necessary that ultraviolet radiation of 354 nm falls on the surface.

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The formal beginning of psychology occurred in Germany and the United States by which two men ?
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Answer: Two men who helped in the development of psychology in Germany was Wilhelm Wundt, and in United States was William James.

Explanation:

Wilhelm Wundt was a German scientist, who was the first person who introduced psychology. He studied the conscious experience as a part of scientific study. It emphasis the identification of the components of the consciousness. Introspection is the process through which conscious experiences can be analyzed.

William James was a scientist, native of U.S. His purpose was to study the function of behavior all over the world. This perspective was known as functionalism. This emphasizes over the fact that how mental activities helps how organisms fit into its surrounding environment.

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4 years ago
A 10.0g piece of copper wire, sitting in the sun reaches a temperature of 80.0 C. how many Joules are released when the copper c
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Answer:

150.8 J

Explanation:

The heat released by the copper wire is given by:

Q=mC_s \Delta T

where:

m = 10.0 g is the mass of the wire

Cs = 0.377 j/(g.C) is the specific heat capacity of copper

\Delta T=40.0 C - 80.0 C=-40.0 C is the change in temperature of the wire

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Q=(10.0 g)(0.377 J/gC)(-40.0^{\circ})=-150.8 J

And the sign is negative because the heat is released by the wire.

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Why do we feel cool when we spray perfume in our body​
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Points P and Q are located at (0, 2, 4) and (-3, 1,5). Calculate
Akimi4 [234]

Answer:

a) The position vector of P is \vec P =(0, 2,4).

b) The distance vector from P to Q is \overrightarrow{PQ} = (-3,-1,1).

c) The distance between P and Q is \|\overrightarrow{PQ}\|=\sqrt{11}.

d) A vector parallel to PQ with magnitude of 10 is \vec v = \left(-\frac{30\sqrt{11}}{11},-\frac{10\sqrt{11}}{11}, \frac{10\sqrt{11}}{11} \right).

Explanation:

a) The position vector of a point is the vector displacement from the origin to the location of the point. That is:

\vec P = (0,2,4)-(0,0,0)

\vec P = (0-0, 2-0, 4-0)

\vec P =(0, 2,4)

The position vector of P is \vec P =(0, 2,4).

b) First, we calculate the position vector of point Q:

\vec Q = (-3,1,5)-(0,0,0)

\vec Q = (-3-0,1-0,5-0)

\vec Q =(-3,1,5)

The distance vector from P to Q is define by the following vectorial expression:

\overrightarrow{PQ} = \vec Q - \vec P (1)

\overrightarrow{PQ} = (-3,1,5)-(0,2,4)

\overrightarrow{PQ} =(-3-0,1-2,5-4)

\overrightarrow{PQ} = (-3,-1,1)

The distance vector from P to Q is \overrightarrow{PQ} = (-3,-1,1).

c) There are two approaches to calculate the distance between P and Q:

First Method - Pythagorean Theorem:

\|\overrightarrow{PQ}\| = \sqrt{(-3)^{2}+(-1)^{2}+1^{2}}

\|\overrightarrow{PQ}\|=\sqrt{11}

Second Method - Dot Product:

\|\overrightarrow{PQ}\| = \sqrt{\overrightarrow{PQ}\,\bullet\,\overrightarrow{PQ}} (2)

\|\overrightarrow{PQ}\| = \sqrt{(-3,-1,1)\,\bullet (-3,-1,1)}

\|\overrightarrow{PQ}\|=\sqrt{11}

The distance between P and Q is \|\overrightarrow{PQ}\|=\sqrt{11}.

d) To determine a vector parallel to PQ with a given magnitude is determined by the following expression:

\vec v = \frac{k}{\|\overrightarrow{PQ}\|} \cdot \overrightarrow{PQ} (3)

Where k is the scale factor.

If we know that \overrightarrow{PQ} = (-3,-1,1), \|\overrightarrow{PQ}\|=\sqrt{11} and k = 10, then the vector is:

\vec v = \frac{10}{\sqrt{11}}\cdot (-3,-1,1)

\vec v = \left(-\frac{30}{\sqrt{11}},-\frac{10}{\sqrt{11}},\frac{10}{\sqrt{11}}\right)

\vec v = \left(-\frac{30\sqrt{11}}{11},-\frac{10\sqrt{11}}{11}, \frac{10\sqrt{11}}{11} \right)

A vector parallel to PQ with magnitude of 10 is \vec v = \left(-\frac{30\sqrt{11}}{11},-\frac{10\sqrt{11}}{11}, \frac{10\sqrt{11}}{11} \right).

8 0
3 years ago
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