# What is Gap: Definition and 288 Discussions

Gallium phosphide (GaP), a phosphide of gallium, is a compound semiconductor material with an indirect band gap of 2.24 eV at room temperature. Impure polycrystalline material has the appearance of pale orange or grayish pieces. Undoped single crystals are orange, but strongly doped wafers appear darker due to free-carrier absorption. It is odorless and insoluble in water.
GaP has a microhardness of 9450 N/mm2, a Debye temperature of 446 K (173 °C), and a thermal expansion coefficient of 5.3 ×10−6 K−1 at room temperature. Sulfur, silicon or tellurium are used as dopants to produce n-type semiconductors. Zinc is used as a dopant for the p-type semiconductor.
Gallium phosphide has applications in optical systems. Its static dielectric constant is 11.1 at room temperature. Its refractive index varies between ~3.2 and 5.0 across the visible range, which is higher than in most other semiconducting materials.

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1. ### Finding Gap Between Two Objects on Moving Conveyor

I am needing to find the gap between two pieces of wood on a conveyor belt. I am new t this and am having trouble knowing what to Google to find the right formulas. I found one answer on here that helped a little, but it was dealing with two conveyors, and I am not sure if I adjusted the formula...
2. ### Admissions Academics gap: Looking for 2nd M.Sc Physics degree or a PhD Physics?

Hi everyone, I finished M.Sc Physics by "Research" at a UK university during the academic year of 2015. I am an international student from India. As I did not do well in my oral presentation defending my M.Sc thesis (but it was not worst), as a result, I got a pass degree. Before the day or...
3. ### I Defining the Prime Gap function

Hi PF! I created a function ##R(x)## that gives the gap between the largest two primes less than or equal to ##x##. To define it, I used this property: $$\pi(x+R(x))=\pi(x)+1$$ Which is true since the ##x## distance between ##\pi(x)## and ##\pi(x)+1## is ##R(x)##. If we solve for ##R(x)## we...
4. ### What is the effect of a 1 cm gap on the magnetic field in a solenoid?

Hey, I was trying to figure out this problem. I got (a) using B = mu * NI/L but I'm not sure how to start the part about the magnetic field in the gap after the solenoid is ripped in half with 1 cm gap. Thanks for the help!
5. ### I Gap between introductory physics & solid state physics?

The left pic is the initial state and the right pics are 2 different descriptions for a metal under electric field E. Are the 2 on the right contradictory and which is correct?
6. ### Studying What to do in a gap year to prepare for a Physics + Math degree

As the title says, I am now in a Coronavirus induced gap year. I have been accepted at a university, which for some reason requires us to do a double major. Hence I chose math as my second major alongside Physics since it has the most overlap, and I'm also very interested in theory. In school, I...
7. ### Engineering Can the efficiency of a solar cell with a single band gap reach 100%?

I have tried looking up online with the photoelectric effect, it just mentioned the energy of the photon must have to equal to band-gap energy. Yet, it didn't mention if 100% can be reached in that case, or if a single bandgap makes any effect...
8. ### An accurate method to determine the band gap

Summary:: What is an accurate method to determine the band gap? What is an accurate method to determine the band gap?
9. ### Admissions Applying for PhD with Low UG GPA and Gap Years

Hey everyone, I'm currently in my master's program in India and have been thinking about applying to states for a phd. So my problem is that I really messed up in my undergrad (2.74/4.00) but I'm doing much better in my MSc (3.2 in 1st sem, will try to reach 3.5 in total). Also, apart from that...
10. ### How to make the most of a gap year during the Covid-19 era?

How to make the most of a gap year during the Covid-19 era? =========================================================== Hello Everyone, Thanks for reviewing my thread. I am opening this thread to get insights into my future prospects for a career in Physics in the era of Covid-19. I...
11. ### I Importance of the energy gap in electronic transport properties

In the solid state physics by Ashcroft & Mermin, in chapter 9 there is a paragraph that I would be grateful if anyone could explain it more for me. The paragraph is: As it said in chapter 12 it will be seen. I read chapter 12 but unfortunately I can't understand what exactly it want to say...
12. ### How to Measure and Calculate Band Gap of a Photovoltaic Device

Hi there! I bought a photovoltaic cell. I would like to learn its band gap at 300 K and 0 K. How can i measure band gap or calculate? I have already measured Temperature to Vmax values. I couldn't find any good information about this topic. Thanks.
13. ### Modeling Uniform Field Gap Electrodes, Rogowski or others

Hi, I am trying to design uniform field gap electrodes using the Rogowski profile. I've read some papers on it, but I'm completely new to this and I am just having a hard time translating what's in the paper to my Matlab code to produce the same results. I'm not sure if this is the right place...
14. ### Uniform Field Gap (Rogowski profile) Electrode Design

Hi, I am interested in designing an electrode that reduces the peak e-field intensity at the edges of the electrode. I've read some papers and it looks like there are quite a few. I'm not really familiar with the terms, so I decided to start off with what looks like is one of the simpler ones...
15. ### Chemistry HOMO-LUMO energy gap of compounds

According to me Option A is a correct option because as the energy difference between two atomic orbitals increases, their interaction, and thus the value of E (or E*) decreases. Here, E is the energy difference between the bonding molecular orbital and the atomic orbital of lower energy , while...
16. ### Gap in the market for a book on the Standard Model

Summary:: Is there a primarily non-technical book covering all aspects of the Standard Model of particle physics? The Standard Model comes up a lot in YouTube videos. There must be a decent amount of public interest. I think there would be a market for a semi-technical but accessible for the...
17. ### Energy band gap when there is an electric field

So I have just been taught this topic but this question seems to be one of a kind and I can't seem to figure it out. What I've learnt: When there is a positive electric field applied to the right, for example, the electrons that are free moving in a crystal (aka conducting band) will oppose...
18. ### I Where exactly is the Hertzsprung Gap?

There seem to be a lot of gaps in this figure, although some streamlined depictions of the figure show a void in the shape of a thin near-right rectangle with its sides as the hypotenuse on the bottom left being the main line, the major on the top being the supergiants, and the minor on the...
19. ### Insight into the conceptual gap and how to fill it

I recently started volunteer math tutoring in an after school program in a city near me. This is one of the poorest cities in the state, and the students' math preparation is about as bad as you'd expect. The after school program is not part of the school system, it's run by a non-profit. I work...
20. ### Engineering Calculating the gap of a parallel plate capacitor

I've been given this question for my TMA2, I've tried looking at the learning material but it gives no information on how to calculate the gap? Does anyone have a formula for this? Or can someone point me in the right direction? Thanks
21. ### Mercury Seal Gap Size: Is it Possible?

I am wondering about the physical properties of mercury. I know that different materials have different density and ability to penetrate small openings. I wonder if I have a small container of mercury, say about 100 grams or less, and there is a small flat opening at the bottom of such container...
22. ### Why is the band gap in alloys such as GaAs less?

In pure crystals,such as,in silicon and germanium,the band gap is more than that in compound semiconductors,such as,GaAs.Why is that so.
23. ### How to optimize spark gap Tesla coils

My elementary school had its first annual science fair a few weeks ago, so me and my friend signed up and we decided to do it on wireless electricity. So naturally, we built a tesla coil. It took a couple of tries, but we eventually got it to barely illuminate a portion of a fluorescent light...
24. ### How to optimize spark gap Tesla coils?

My elementary school had its first annual science fair a few weeks ago, so me and my friend signed up and we decided to do it on wireless electricity. So naturally, we built a tesla coil. It took a couple of tries, but we eventually got it to barely illuminate a portion of a fluorescent light...
25. ### Stargazing What explains the Luna impact gap?

I was reading in Sky and Telescope about the Lunar flash during the eclipse last week, and looking at the impact map (2005-2018) I was wondering why there is a 'gap' with no impacts down the middle. It seems rather unlikely that there would be no 'hits' here. Is this an artifact of the limb and...
26. ### B The Spectral Gap and Quantum Vacuum Fluctuations

Hello. Recently Scientific American magazine carried an article about the work of the authors of this paper. https://arxiv.org/abs/1502.04573 The Undecidability of the Spectral Gap. The SciAm article is linked to here -...
27. ### Schools I'm forced to take a gap before uni, how will it affect me?

Hi. I am an 18-year-old guy who graduated HS last July with an average of 88%. I studied AP Physics C, AP Calculus AB and took a uni-level class in Energy physics, among other science and engineering related courses like Java programming, Autocad and Inventor. I Also worked with my country's...
28. ### A Band Gap Vs Pressure: Proskite Compounds

why band gap reduces when pressure increased for provskite compounds ? Nawzad
29. ### I Closing the Gap: The Evolution of CMS at CERN

In this picture of CMS, there is a huge gap between the two sides. There is no way that the collision occur directly in midair right? So is the gap already been sealed? ( which means the picture was taken before it started to operate) Or I am completely wrong?
30. ### A Energy gap between energy bands in solid state physics

I know that Bragg reflection in solid states at the edge of e.g. the first Brillouin Zone causes standing waves at these edges, which creates a gap between the energy bands. In this picture below you can see the probability density of a symmetric (+) and anti-symmetric (-) standing wave. The...
31. ### Admissions A gap in biography in application

I am the second year Master student and I'm planning to apply for PhD this fall. My goal are top schools in the USA and my chances l seem to be pretty good overall (6 published articles, 4 of which are in decent international physics journals like PRB/APL; excellent pGRE and GRE scores, four+...
32. ### Toroid with Air Gap magnetostatics problem

Homework Statement consider a toroidal electromagnet with an iron ring threaded through the turns of wire. The ring is not complete and has a narrow parallel-sided air gap of thickness d. The iron has a constant magnetization of magnitude M in the azimuthal direction. Use Ampere's law in terms...
33. ### Air resistance: cylindrical rotor in stator with air gap

Hello, I am currently doing research on the aerodynamic properties of a rotating cylinder in a cylindrical housing. The cylinder represents a rotor in a electric motor. The air gap between rotor and stator is about 0.5mm. I'm looking for a theoretical analysis and calculation on the...
34. ### Other Gap Year Physics Research for an International Student?

Just got rejected by nearly all of my grad schools (one hasn't reply but the chance is pretty small). The funding is super harsh this year in my field and even worse for a student from China. Is there any way for an international student to take a gap year for physics research in the U.S? ( My...
35. ### Magnetic field in the gap of a tapered torus

Homework Statement Consider a toroidal electromagnet filled with a magnetic material of large permeability µ. The torus contains a small vacuum gap of length h. Over most of its length the torus has a circular cross section of radius R, but towards the gap the torus is tapered on both of its...
36. ### Energy Gap of 2 states in a deep rectangular potential well.

What is the energy gap between the ground state (n=0) and the first excited state (n=1) of an electron trapped in a deep rectangular potential well of width 1Å?
37. ### Is Plate Capacitor Gap a "Non-linear" Medium?

Could the space (air gap) between two DC charged parallel plates be considered to be a "non-linear" medium with respect to an EMF radiated by a coil contained within that space?
38. ### Studying I'm 16 and want to study physics, should i take a gap year?

I was fascinated with physics since i was 14, when i actually began my learning journey, i got into Newtonian mechanics and eventually learned some electronics and programming. Noticing the math that was involved, i decided to first get started with math before i proceed into learning physics...
39. ### I Relationship between the depletion region and the band gap of a diode?

Hi, Lately I've been reading about a lab exercise in which Planck's constant is estimated using LEDs. Every procedure I've encountered states that the energy of an emitted photon (and by extension the potential across the semiconductor's band gap) is equal to the threshold voltage multiplied by...
40. ### Semiconductor resistor in series with a capacitor -- Energy gap

Homework Statement Consider a circuit that consists on a resistor of an intrinsic semiconductor R and a capacitor C in series. The voltage between the terminals of the circuit is U, which is an alternated sinusoidal voltage. U1, which is the voltage in the capacitor as a phase difference of 30...
41. E

### MMF/Flux density across air gap for a salient pole

Hi I am trying to understand the figure 2 I have attached to this post. From text: Ok, I get that the air-gap flux density varies in a sinusoidal manner, because the air gap length is not constant i.e. non-constant reluctance and hence non-constant magnetic flux density. What I do not...
42. ### Other What's the Best Physics Textbook for a Gap Year Review?

Hi, I've just finished A Level Physics, and after a gap year I'm headed to do Physics at Exeter. I'm looking for a textbook or online course or something that has lots of A Level and (maybe slightly higher) Physics questions that I can work through over the course of this year. Does anyone have...
43. ### Efficient Use of Spectrum: The Importance of a Safe Gap Between Channels

If we have 300kHz bandwidth and every channel uses 100kHz BW, then theoretically we can have total of 3 channels that won't overlap. Why do we need to assign some of the bandwidth for "safe gap" between channels if they "don’t" overlap?
44. L

### Astronomy/Astrophysics Gap Year/5th year of Undergrad

Hello there, I am currently a senior undergraduate Astronomy and Astrophysics major at Villanova University. With the GRE and graduate school applications coming up I have been wondering if it would be beneficial for me to either take a gap year or to possibly take a 5th year of undergraduate...
45. ### Schools Should I take a gap year to self study before college?

I was admitted to a very good undergraduate physics program (Columbia University), but I think I would like to take a gap year (defer my admission) to prepare my self better. I do feel a bit intimidated as I come from Colombia and I would prefer it if I could further my studies before going to...
46. ### Energy gap between orbitals and stability

We know that the lower the energy gap between bonding and antibonding orbital the easier it is to break the bond making it unstable. However, in a conjugated double bond, the overlapping of wavefunctions cause the energy gap between the bonding and antibonding orbital go down. Then why...
47. ### What if gap is irregular in capacitor

I don't have clear concept on voltage. I am a Mechanical guy. If the gap is irregular in large capacitor, how voltage is derived in theory. Using software I can divide the surface into many pieces and calculate voltage of individual small piece. I attached my problem.
48. ### Flux and Current of Magnetic Core With Air Gap

I am a student of electrical engineering. This task appears in our textbook. However, there were no solutions provided. I tried understanding the task but got lost in the process. This is why I seek help here on this site. I would like to ask you for guidance and any sort of advice on how to...
49. ### Physics 2 year gap after M.Sc , now want to do Ph.D

I need help. I completed my post graduation in 2015 material science, now it nearly 2 year gap want to do Ph.D . How can i start . i don't have GATE score, how can i apply for Ph.D.
50. ### A Nanowire with charge neutrality in band gap

I'm working on a finite element simulation of the electrostatic potential V(r) in and around semiconductor nanowires, based on solving Poisson's equation. While the details of the problem will follow shortly, the crux of where I run into trouble is that for nanowires it is important to include...