# A few questions on quantum mechanic and photoelectric effects

• anderson1
In summary, the de Broglie wavelength equations uses momentum, not mass, to calculate the wavelength.
anderson1
Hi all,

I have a total of 6 questions, 3 of them are posted here and 3 of them are provided in the link because they involve graphs.

1. KE of an electron is twice that of a proton, what is ratio of de broglie wavelength of proton:electron?
My answer: since de broglie wavelength is lamba = h/mu. I put in all the values and mass of electron and proton. In the end, I get the answer as 0.00109. But I wish someone can help me double check to see if my answer is correct.

2. If given work function of a metal, eg 2 Joules. And given wavelength of a photon to be eg, 5 meter. how to find stopping voltage? In another word, if given wavelength (in meter) and work function (in Joules), how to find stopping voltage (in Volt)?
My answer: I am unsure of this question because I am unsure about the relationship between wavelength, stopping voltage and work function. Is it c/hλ + work function = stopping voltage?

3. A spherical molecule has mass "M" kg and diameter of "D"nm. The uncertainty in position is equal to the diameter. What is the minimum speed of the molecule?
My answer: This question I don't really know. I think it involves heinsberge uncertainty principle. Anyone can enlighten me?

4. http://i42.tinypic.com/2pzmq38.png
My answer: My educated guess is option B because since both source one and two have same wavelength, starting applied voltage should be same. But I do not understand why graph of source II is higher than graph of source I. Please tell me if my answer is correct or wrong and explain your answer in detail.

5. http://i44.tinypic.com/214pi61.png
My answer: My guess is option 4. It is related to question 4. If someone can explain question 4, i think i can do this question. Please tell me if I am wrong or correct, and why.

6. http://i42.tinypic.com/ka4j8k.png

For all questions, please provide an answer and tell me why you think it is the answer. Explanation is key.

momentum = mass multiple velocity..

so i just break it up? Did i do it wrongly? =.=

## 1. What is quantum mechanics?

Quantum mechanics is a branch of physics that studies the behavior of particles at a microscopic level, including atoms, subatomic particles, and photons. It describes how these particles interact with each other and with energy.

## 2. What is the photoelectric effect?

The photoelectric effect is a phenomenon where light (or other electromagnetic radiation) incident on a material surface causes the ejection of electrons from the surface. This effect was first observed by Albert Einstein and is explained by the particle-like nature of light.

## 3. How does quantum mechanics explain the photoelectric effect?

Quantum mechanics explains the photoelectric effect by treating light as a stream of particles, called photons. When photons hit the surface of a material, they transfer their energy to electrons, allowing them to overcome the binding forces of the material and be ejected.

## 4. What is the significance of the photoelectric effect?

The photoelectric effect has significant implications in fields such as electronics, solar energy, and quantum physics. It also played a crucial role in the development of quantum mechanics and the understanding of the particle-wave duality of light.

## 5. Can the photoelectric effect be observed in everyday life?

Yes, the photoelectric effect can be observed in everyday life. For example, solar panels use the photoelectric effect to convert sunlight into electricity. It is also the basis for the functioning of photodiodes in cameras and other light sensors.

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