General Physics III - Chapter 1, Lecture notes of Physics

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General Physics 3

➢ Syllabus

➢ Teaching strategy

INTRODUCTION

Syllabus and teaching strategy

Lecturer: VU THI HANH THU, Associate Professor. Dr Phone: 09455 99999 Department Of Applied Of Physics, Faculty Of Physics & Engineering Physics, University Of Sciences Ho Chi Minh City Viet Nam Email: vththu@hcmus.edu.vn Facebook: Thu Vu (search mail thinfilmvacuum@yahoo.com) Office: Department Of Applied Of Physics, A Building Vacuum Laboratory, F Building, Room 14 (F14) Grading: Midterm examination: 25%; Final examination: 50% (multi - choice) In-class exercises and Plus/Quizzes: 25% (Ms Ngân, the teaching assistant ) (Plus/bonus: max 10%) Syllabus: See Syllabus.doc Textbooks: Serway & Jewett, Physics for Scientists and Engineers with Modern Physics, 9th edition, Brooks/Cole, 2014.

Lecture 1

Chapter 35. The Nature of Light and the principles

of ray Optics Light and Optics

35.1 The Nature of Light 35.2 Measurements of the Speed of Light 35.3 The ray approximation in ray Optics 35.4 Analysis Model: Wave Under reflection 35.5 Analysis Model: Wave Under refraction 35.6 Huygens’s principle 35.7 Dispersion 35.8 Total Internal reflection

INTRODUCTION TO LIGHT

Light is basic to almost all life on the Earth. Light is a form of electromagnetic radiation. Light represents energy transfer from the source to the observer. Many phenomena depend on the properties of light. ◼ Seeing a TV or computer monitor ◼ Blue sky, colors at sunset and sunrise ◼ Images in mirrors ◼ Eyeglasses and contacts ◼ Rainbows ◼ Many others

Before the beginning of the nineteenth century,

light was considered to be a stream of particles.

The particles were either emitted by the object

being viewed or emanated from the eyes of the

viewer.

Newton was the chief architect of the particle

theory of light.

◼ He believed the particles left the object and stimulated the sense of sight upon entering the eyes.

35.1. The Nature of Light

35.1. Nature of Light – Alternative View

Christian Huygens argued that light might

be some sort of a wave motion.

Thomas Young (in 1801) provided the first

clear demonstration of the wave nature of

light.

◼ He showed that light rays interfere with each

other.

◼ Such behavior could not be explained by

particles.

Confirmation of Wave Nature

During the nineteenth century, other developments

led to the general acceptance of the wave theory of

light.

Thomas Young provided evidence that light rays

interfere with one another according to the principle

of superposition.

◼ This behavior could not be explained by a particle theory.

Maxwell asserted that light was a form of high-

frequency electromagnetic wave.

Hertz confirmed Maxwell’s predictions.

Particle Nature

Some experiments could not be explained by the wave model of light. The photoelectric effect was a major phenomenon not explained by waves. ◼ When light strikes a metal surface, electrons are sometimes ejected from the surface. ◼ The kinetic energy of the ejected electron is independent of the frequency of the light. Einstein (in 1905) proposed an explanation of the photoelectric effect that used the idea of quantization. ◼ The energy of a photon is proportional to the frequency of the electromagnetic wave ◼ The energy of a photon E = hƒ h is Planck’s Constant and = 6.63 x 10-^34 J.s

Nature of Light

35.2. Measurements of the Speed of Light

Since light travels at a very high speed, early attempts to measure its speed were unsuccessful. ◼ Remember c = 3.00 x 10 8 m/s Galileo tried by using two observers separated by about 10 km. ◼ The reaction time of the observers was more than the transit time of the light.

Roemer’s Method, cont.

The periods of revolution were longer when the Earth was receding from Jupiter. ◼ Shorter when the Earth was approaching Using Roemer’s data, Huygens estimated the lower limit of the speed of light to be 2.3 x 10 8 m/s. ◼ This was important because it demonstrated that light has a finite speed as well as giving an estimate of that speed.

Roemer’s Method

Fizeau’s Method, cont.

d is the distance between the wheel and the mirror. Δt is the time for one round trip. Then c = 2d / Δt Fizeau found a value of c = 3.1 x 10 8 m/s.

Fizeau’s Method