100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Previously searched by you
Previously searched by you
logo
PHY 250 General Physics: Exam Questions and Answers Latest Update 2023/2024 | Graded A+ | Straighterline $17.99
Add to cart
Quickly navigate to
Preview
  2.  
  3. PHY 250
  4.  
  5. PHY 250

Exam (elaborations)

PHY 250 General Physics: Exam Questions and Answers Latest Update 2023/2024 | Graded A+ | Straighterline
 0 purchase
  • Course
  • PHY 250
  • Institution
  • PHY 250

PHY 250 General Physics: Exam Questions and Answers Latest Update 2023/2024 | Graded A+ | Straighterline

Preview 3 out of 21  pages

Document information

  • October 28, 2024
  • 21
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers

Subjects

  • phy 250
  • phy 250 general physics
  • phy 250 general physics exam questions and answer

Written for

  • PHY 250
All documents for this subject (22)

Seller

avatar-seller
tutorsection1

Reviews received

Content preview

PHY 250 General Physics: Exam Questions and Answers Latest Update
2023/2024 | Graded A+ | Straighterline


HW1. A slow freight train chugs along a straight track. The distance it has traveled
after x hours is given by a function g(x). An engineer is walking along the top of the
box cars at the rate of 6 km/hr in the same direction as the train is moving. The
speed of the man (in km/hr) relative to the ground is: - ANSWER g'(x) + 6

v(Eng/Ground) = v(Eng/Train) + v(Train/Ground)

HW2. Explain why accelerating charges generate light but charges that are
stationary or moving at a constant velocity do not. - ANSWER NOTICE Light is a
wave: an oscillation in time and space of the E and B fields.
A stationary charge produces a time dependent E-field.
A constant velocity charge constitutes a current and produces a time-independent B-
field.
Therefore it is necessary for a charge to accelerate to produce light.
Note: One can do work on a charge by "dragging" it through an E-field at
CONSTANT velocity. Thus, in general, doing work on a charge is NOT enough to
guarantee production of light!

HW2. It is the thermal motion of charged particles at the sun's surface that produces
the electromagnetic radiation emitted by the sun (use c=3.0 E8 m/s). To generate a
blue light at 400nm, at what frequency would a charged particle have to be vibrating
back and forth? - ANSWER f = c/lambda = 7.5e14 Hz

HW2. It is the thermal motion of charged particles at the sun's surface that produces
the electromagnetic radiation emitted by the sun (use c=3.0 E8 m/s). To generate a
blue light at 400nm, a charged particle have to be vibrating back and forth at a very
high frequency.
Even in the most advanced circuits, we cannot oscillate electrons back and forth at
that rate through wires. But we can oscillate charges back and forth quickly enough
to broadcast TV using radiowave signals. At what frequency does that electronics at
the TV station need to have the charges oscillate back and forth on a TV broadcast
antenna to transmit a typical TV signal (say a radiowave transmission signal with a
wavelength of 3 meter)? - ANSWER f = c/lambda = 3.0e8/3 = 10e8 Hz = 100 MHz

Learning Goal (May 08 Lecture): Write down the mathematical description of a
classical electromagnetic wave, and relate the terms in the expression to the
velocity, wavelength,
and frequency of the wave. - ANSWER

Learning Goal (May 08 Lecture): Describe the energy in a classical EM wave in
terms of the amplitude of the wave, and describe quantitatively what happens when
an EM wave is absorbed by a material if the wavelength is long enough and intensity
high enough that it behaves classically. - ANSWER

,HW2. When we were discussing the classical wave-view of electromagnetic light, we
considered the following scenario where 3 different beams of laser light (single-
frequency light) were hitting 3 barrels filled with water. The drawing showed the
frequency and amplitude of the electromagnetic wave in each case (the amplitude
for #1 and #2 are the same). The clicker question compared how fast the barrels will
heat. T or F: The total amount of power hitting barrel #1 is less than the total amount
hitting barrel #2. - ANSWER False
The power is proportional to the maximum E-field multiplied by the effective surface
area in contact with the light. Since this area is the same for both barrels, as well as
Emax, the power must be the same.

(May 10 Lecture): T or F. The amount of energy in each photon hitting barrel #1 is
the same as the amount in each photon hitting barrel #3. - ANSWER True

The two waves have the same wavelength and hence the same frequency (f*lamba
= c). Thus E(photon) = hf is the same in both cases.

(May 10 Lecture): T or F. The number of photons hitting barrel #1 per second is the
same as the number of photons hitting barrel #2 per second. - ANSWER False

The total number of photons hitting the barrel per unit time multiplied by the energy
per photon is actually the total power delivered. These waves have the same power
but different frequency and hence different energy per photon. Therefore, the
number of photons hitting the barrels must be different.

(May 10 Lecture): T or F. Barrel #1 and #2 heat up at the same rate. - ANSWER
True

The rate of heating must be proportional to the power, since this is the energy
delivered per unit time. These waves have the same power.

(May 10 Lecture): From the picture you can see that, (wavelength of #2) = 3/5
(wavelength of #1). If there are 2,500,000 photons per second hitting barrel #2, how
many photons are hitting barrel #1 per second? - ANSWER Power = (number of
photons(n)*energy of photon(E))/change in time(dt)

Here dt = 1 second
E = hf

We know P1 = P2
n1E1/dt = n2E2/dt

n1 = n2*(hf2/hf1) = n2*(lambda1/lambda2)

n2 = 2500000

n1 = 250000*(5/3)

, HW2. A photoelectric-effect experiment finds a stopping potential of 1.93 V when
light of 200 nm is used to illuminate the cathode. From what metal is the cathode
made? (hint, use table 39.1 in Knight Volume 5) - ANSWER Aluminum

The stopping potential must be the right strength to stop even the most energetic
electrons, which have energy E(photon) - E.

So we need Vstop = W/e = deltaKEmax/e = (Ephoton-E0)/e = (hf-E0)/e

E0 = hf-eVstop = 4.27

HW2. A photoelectric-effect experiment finds a stopping potential of 1.93 V when
light of 200 nm is used to illuminate the cathode. The intensity of the light is doubled.
What is the stopping potential now? - ANSWER The stopping potential depends only
on frequency, work function, and change of electron, NOT on intensity!

Stationary Charges - ANSWER constant E-field, no magnetic (B)-field
(We don't see charges glow in the dark)

Charges moving at a constant velocity - ANSWER Constant current through wire
creates a B-field
but B-field is constant. (We don't SEE DC.)

Accelerating charges - ANSWER changing E-field and changing B-field
(EM radiation...both E and B are oscillating)
We talked briefly about Maxwell equations

HW5. The process where a photon hits an atom that is already in a higher energy
level and this causes the atom to spit out a photon that is identical to the one that hit
the atom resulting in two identical photons - ANSWER Stimulated emission

The fact that a passing photon stimulates the atom to emit another photon explains
the name of this process

HW5. The process by which the light is absorbed and the energy causes the atomic
electron to go to a higher energy level - ANSWER Absorption

If an electron jumps to a higher energy state, it must have absorbed a photon

HW5. The process in which the electron naturally jumps down from a higher energy
state to a lower state and spits out a photon corresponding to the energy difference
as it does so - ANSWER Spontaneous Emission

If the electron jumps down on its own, without being influenced by a passing photon,
it is called spontaneous emission

HW5. A laser is created by producing a lot of photons created by stimulated
emission. What characteristics make light produced by stimulated emission so
special compared to light produced through spontaneous emission? - ANSWER -
Photons' electromagnetic waves are oscillating exactly in phase.

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller tutorsection1. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $17.99. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

63950 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 15 years now

Start selling

Recently viewed by you

Exam (elaborations) ·

(0)

NURS-6512N-53,Advanced Health Assessment.2021 Summer Qtr Midterm Exam - Week 6 (100 out of 100 points)  

Exam (elaborations) ·

(0)

NUR 1290 Final Exam Questions with 100% Correct Answers | Latest Version 2024 | Expert Verified | Ace the Test

Exam (elaborations) ·

(0)

Solutions for Classical and Modern Numerical Analysis, 1st Edition by Ackleh (All Chapters included)

Exam (elaborations) ·

(1)

Official summer 2024 AQA GCSE CITIZENSHIP STUDIES 8100/2 Paper 2 Merged Question Paper + Mark Scheme

Class notes ·

(0)

University of Central Florida - MAC 1114C - 5.5 Inverse Trigonometric Functions and Their Graphs Notes - Kwon

Exam (elaborations) ·

(0)

Portage Pathophysiology Module 1 to 10 Exam (2024 / 2025) Questions and Verified Answers, 100% Guarantee Pass

Exam (elaborations) ·

(0)

OCR 2023 GCE Physics A, Exploring physics: H556/02 (A Level) Paper (Questions with Mark Scheme combined)

Exam (elaborations) ·

(1)

Liberty University HSCO 506 Quiz 3 Prayer and Christian Counseling answers perfection A+ Guarantee:

Exam (elaborations) ·

(0)

Georgia Pesticide Applicators Exam (Cat 24 And General Standards (Commercial))with Complete Solutions

$17.99
  • (0)
Add to cart
Added