BlogPhysicsGuide to HSC Physics Module 7: The Nature of Light

# Guide to HSC Physics Module 7: The Nature of Light

Feeling lost with HSC Physics Module 7: The Nature of Light?

Don’t sweat it, we’re here to help!

This topic is all about what makes our world brighter every day – light! Whether we get it from the sun, from electrical devices around us or from this very screen you’re reading this article on, light is everywhere and it’s important you know how it works.

In this article, we’ll break down each of the inquiry questions for you, talk you through changes from the old Module 7, as well as tips to getting a Band 6 in this topic!

So, what are you waiting for? Let’s jump right in!

## Changes from the Old Modules

This topic is a combination of topics from the old syllabus (Space and Ideas to Implementation).

The bulk of this topic is based on the nature of light discussed through the Photoelectric Effect and Black Body Radiation features of the old Topic 3. However, Einstein’s equations make a large appearance as we dive into Relativity at the back end of this topic from the previous Topic 1.

Also, as with most of the Physics syllabus, a focus more on depth is also present in this topic of the new syllabus, including diffraction gratings, the plane polarisation of light and Newton’s and Hyguen’s Laws.

## What’s there to Learn in HSC Physics Module 7?

Let’s enlighten you by showing what there is to learn in this new topic;

1. You take a walk down memory lane, discussing the electromagnetic theories
2. You enjoy the classics, such as the original wave model of light
3. You look at how we use light, in the form of spectra, to investigate other areas of science such as astronomy.
4. You begin to bend your mind, as we discuss the quantum area of light and how light has a dual personality
5. Finally, we wrap up the course with the most mind-boggling topic of relativity, as time, mass and length all behave differently at very high speeds.

## Overview of HSC Physics Module 7

### Inquiry Question 1: What is Light?

Firstly, you look back at the history of light and how it has been looked at.

You look at how Maxwell’s contributions united electricity and magnetism to electromagnetic waves and how these waves all travel at a constant speed, the speed of light, whilst in a vacuum.

You discuss how electric and magnetic waves vibrate perpendicular to one another in the direction of travel, plus the different instruments that both send and receive radio waves.

You recount the classical ways of how we determined the constancy of the speed of light and we also look at the usefulness of light in identifying elements and through identifying the colour, density and surface temperature of stars through the use of spectroscopy.

### Inquiry Question 2: What evidence supports the classical wave model of light and what predictions can be made using this model?

Next, you consider the wave nature of light, how we have always considered it in classical physics.

You discover how diffraction occurs and we measure quantitatively the phenomenon of interference through using light travelling through a double slit apparatus and through diffraction gratings.

We continue our investigation with Netwon’s and Hyguen’s law of how light is a wave vibrating upwards and downwards perpendicular to the direction of travel.

You then look at Malus’ Law involving the plane polarisation of light. This uses the relationship Intensity = Maximum Intensity x cos^2(theta) to describe the significance of polarisation in developing a model of light.

We see that when light in the form of a beam is passed through a polariser, the intensity of the light changes depending on the angle the polariser is positioned at in relation to the angle that produces maximum intensity.

### Inquiry Question 3: What evidence supports the particle model of light and what are the implications of this evidence for the development of the quantum model of light?

Continuing, you dive into the mind-bending world of the quantum model of light, resulting from the particle-like features of light.

You see how Planck determined that the energy from light is proportional to its frequency and how his work led to Einstein determining that light was made of packets of energy.

We also discuss Wein’s law in relation to where the peak occurs in Black Body Radiation diagrams.

You also look at the photoelectric effect to demonstrate inconsistencies in what occurs with the transfer of energy.

This confirmed Einstein’s hypothesis, that as these electrons had a consistent kinetic energy relating to the Planck-Einstein equation and not releasing electrons of all different energies.

### Inquiry Question 4: How does the behaviour of light affect concepts of time, space and matter?

This is where the topic breaks down the barriers of classical physics the most.

You look at how time slows, length contracts and how mass increases as we travel at speeds close to the speed of light. You also notice experiments where these effects have been confirmed.

Length contraction is confirmed by cosmic muons, time dilation is confirmed through the atomic clocks of the Hafele-Keating experiment and particle accelerators see more and more energy needed to accelerate a heavier and heavier proton.

## How to get a Band 6 in HSC Physics Module 7: The Nature of Light

### Tip #1: Prepare to Think Differently

This topic in particular moves away from classical physics of what you have learnt so far.

Be prepared to think differently in to how light has a dual nature and how time, length and mass are not constant at all speeds, where light is (in a vacuum)

### Tip #2: All or Nothing

The concept of quantised energy is difficult to wrap your head around. When energy is transferred, only all or none of the energy is transferred, never a portion of the energy “packet.”

This is why the maximum kinetic energy is constant depending on the wavelength of light used in the photoelectric effect and the work function of the metal used.

This energy also has to be positive and hence not all wavelengths of light eject electrons.

### Tip #3: Longer Time, Shorter Length, Larger Mass

Relativity is another mind-boggling area of this topic.

If you remember some examples of where the 3 effects occur and how to rearrange these equations, you should receive marks as relativity rarely doesn’t appear.

And that wraps up our guide to HSC Physics Module 7: the Nature of Light – good luck!

You can also check out our other HSC Physics guides below:

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Sean Stephen graduated in 2018 with an ATAR of 97.1 and is currently studying a Bachelor of Actuarial Studies / Bachelor of Commerce (Accounting and Finance) at UNSW. Beginning at Art of Smart in 2019, Sean works across the Resource Design, Innovation and Blogging Teams to support thousands of students throughout their HSC. When away from studying, Sean enjoys everything pop culture from videogames to TV, music and movies.

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