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Furkat [3]
3 years ago
14

If the work function of a material is such that red light of wavelength 700 nm just barely initiates the photoelectric effect, w

hat must the maximum kinetic energy of ejected electrons be when violet light of wavelength 400 nm illuminates the material? Express your answer with the appropriate units.
Physics
1 answer:
marishachu [46]3 years ago
3 0

Answer:

2.13 x 10^-19 J or 0.53 eV

Explanation:

cut off wavelength, λo = 700 nm = 700 x 10^-9 m

λ = 400 nm = 400 x 10^-9 m

Use the energy equation

E = \frac{h c}{\lambda _{o}}+K

Where, K be the work function

\frac{h c}{\lambda} = \frac{h c}{\lambda _{o}}+K

K =hc\left ( \frac{1}{\lambda } -\frac{1}{\lambda _{0}}\right )

K =6.63\times 10^{-34}\times 3\times 10^{8}\left ( \frac{1}{4\times 10^{-7} } -\frac{1}{7\times 10^{-7}}\right )

K = 2.13 x 10^-19 J

K = 0.53 eV

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Answer:

D

Explanation:

D) The overall work done by gravity is zero  

This statement is correct .

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5 0
3 years ago
If the mass of an object is 14 lbm, what is its weight, in lbf, at a location where g = 32.0 ft/s2?
mixas84 [53]

Using the formula:

w = m x g ....... eq1

here w is weight of the object.

m is mass of the object, and

g is the acceleration of gravity.

mass, m = 14 lbm (given)

acceleration of gravity, g= 32.0 ft/s^{2}

Now, substituting the values in equation (1):

w = 14lbm x 32.0 ft/s^{2} = 448 lbm ft/s^{2}

since, 1 lbf = 32.174 lbm ft/s^{2}

so, w = 448 x \frac{1}{32.174}

w = 13.924lbf

Hence, the mass of an object is 13.924 lbf.

To know more about such questions, visit:

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3 0
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if a 0.040-kg stone is whirled horizontally on the end of a 60-m string at a speed of 4.4 m/s, what is the centripetal force ? *
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