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strojnjashka [21]
3 years ago
12

Which statement below concerning the photoelectric effect is true? View Available Hint(s) Which statement below concerning the p

hotoelectric effect is true? There is a threshold frequency for each metal, and only light of a frequency higher than this threshold causes electrons to be emitted from the metal surface. Light with a frequency below the threshold frequency can still cause electrons to be emitted from the metal surface, but there will be a lag time while sufficient energy to dislodge the electrons builds up. There is a threshold wavelength for each metal, and only light of a longer wavelength than this threshold causes electrons to be emitted from the metal surface. Increasing the intensity (amplitude) of the light shined on a metal surface is sufficient to cause the emission of electrons from a metal surface.
Physics
1 answer:
kakasveta [241]3 years ago
8 0
There is a threshold frequency for each metal, and only light of a frequency higher than this threshold causes electrons to be emitted from the metal surface.
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The law of universal gravitation states that a gravitational force exists between all objects in the universe. This force is dir
Ber [7]

Answer: D. it has been demonstrated to be without exception under certain stated conditions.

Explanation:

A <u>Law</u> is an affirmation (something established) based on repeated long-term observation of a phenomenon that has been studied and verified.  

That is: A law is present in all known theories and therefore is considered universal. In addition, a law can not be refuted, nor changed, because its precepts have been proven through various studies.  

<u>Unlike theory</u>, which is the set of rules and principles that describe and explain a particular phenomenon and <u>is subject to changes as new evidence emerges that gives meaning to it.  </u>

Then, based on what is explained above, the law of universal gravitation is a statement that exists because it was rigorously tested and verified, therefore it can not be refuted.

3 0
3 years ago
Water flows through a cast steel pipe (k = 50 W m.K, ε = 0.8) with an outer diameter of 104mm and 2 mm wall thickness. Calculate
masha68 [24]

Answer:

The heat loss per unit length is   \frac{Q}{L}   = 2981 W/m

Explanation:

From the question we are told that

     The outer diameter of the pipe is d = 104mm = \frac{104}{1000} = 0.104 m

     The thickness is  D = 2mm = \frac{2}{1000} = 0.002m  

      The temperature  of water is  T = 90^oC = 90 + 273 = 363K  

      The outside air temperature is T_a = -10^oC = -10 +273 = 263K

        The water side heat transfer coefficient is z_1 = 300 W/ m^2 \cdot K

       The  heat transfer coefficient is  z_2 = 20 W/m^2 \cdot K

The heat lost per unit length is mathematically represented as

           \frac{Q}{L}   = \frac{2 \pi (T - Ta)}{ \frac{ln [\frac{d}{D} ]}{z_1}  +  \frac{ln [\frac{d}{D} ]}{z_2}}

Substituting values

         \frac{Q}{L}   = \frac{2 * 3.142 (363 - 263)}{ \frac{ln [\frac{0.104}{0.002} ]}{300}  +  \frac{ln [\frac{0.104}{0.002} ]}{20}}

           \frac{Q}{L}   = \frac{628}{0.2107}

           \frac{Q}{L}   = 2981 W/m

6 0
3 years ago
A descending elevator of mass 1,000 kg is uniformly decelerated to rest over a distance of 8 m by a cable in which the tension i
Stolb23 [73]

The speed  V_{i} of the elevator at the beginning of the 8 m descent is nearly 4 m/s. Hence, option A is the correct answer.

We are given that-

the mass of the elevator (m) = 1000 kg ;

the distance the elevator decelerated to be y = 8m ;

the tension is T = 11000 N;

let us determine the acceleration 'a' by using Newton's second law of motion.

∑Fy = ma

W - T = ma

(1000kg x 9.8 m/s² ) - 11000N = 1000 kg x a

9800 - 11000 = 1000

a = - 1.2 m/s²

Using the equation of kinematics to determine the initial velocity.

V_{f} ² = V_{i}² + 2ay

V_{i} = √ ( 2 x 1.2m/s² x 8 m )

V_{i} = √19.2 m²/s²

V_{i} = 4.38 m/s   ≈ 4 m/s

Hence, the initial velocity of the elevator is 4m/s.

Read more about the Equation of kinematics:

brainly.com/question/12351668

#SPJ4

8 0
1 year ago
Define solar system.<br>Mention 3 types of energy.​
sveticcg [70]

Answer:

The Solar System is the Sun and all the objects that orbit around it

The Sun is orbited by planets, asteroids, comets and other things. ...

It has strong gravity

There are many types of energies

three types are

kinetic energy

potential energy

gravitational energy

4 0
2 years ago
Read 2 more answers
Which one of these wireless technologies are not in the permeable zone of the radio wave spectrum
k0ka [10]

Answer:

Explanation:

3 and 4G networks, Bluetooth, and Wi-Fi technologies. my opinions

4 0
2 years ago
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