## Dependence of nuclear radius on nucleon number

Posted in A2 Unit 5: Radioactivity, AQA A2 Unit 5 by Mr A on 22 Feb 2010

What is the relationship between the radius of a nucleus, R, and the number of nucleons in the nucleus , A (AKA the mass number, N)?

Use the following data to investigate this. Assuming it is a power relationship, recall that we can find the log of both sides in order to discover what this power is.

 Nucleon number, A Nuclear radius, R (fm) 7 2.30 14 2.89 31 3.77 88 5.34 120 5.92 157 6.47 197 6.98 239 7.45

## Diffraction gratings and patterns

Posted in AQA AS Unit 2, AS Unit 2: Waves by Mr A on 21 Feb 2010

Diffraction grating equation

Important: The following derivation assumes that all rays incident on each part of the screen are parallel. This is a fair assumption, provided the distance from the slits to the screen is much larger than the slit separation.

Thus, for the central fringe, the rays travel exactly the same distance as one another.

For the first order fringe, each successive ray travels an extra path difference of $d \sin{\theta}$. Incidentally, this extra path difference must also be equal to $\lambda$, for constructive interference to occur.

If we proceed to the second order fringe, each successive ray must travel an extra $n \lambda$. It, therefore, follows that

$\boxed{n \lambda = d \sin{\theta}}$

Worked example (class demo)

If a red laser is shone through a diffraction grating with ? lines per mm at a screen ? m away, and the first order fringe makes an anlge of ?, what is the wavelength of the light?

## Interference and Diffraction

Posted in AQA AS Unit 2, AS Unit 2: Waves by Mr A on 20 Feb 2010

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## Huygens’ Principle and Wavefronts

Posted in AQA AS Unit 2, AS Unit 2: Waves by Mr A on 7 Feb 2010

• Huygens’ principle
• Diffraction and Reflection
• Refraction

Huygens’ Principle

Given that waves are caused by a source of disturbance, and that waves themselves cause disturbance as they propagate, Christiaan Huygens (1629-1695) treated waves along the principle that:

Every point on a wave may be considered as a point source disturbance, causing secondary waves that spread out evenly in all directions with a speed equal to the speed of propagation of the wave.

Diffraction and Reflection

1)

2)

3)

Refraction

## Finding the Critical Angle

Posted in AQA AS Unit 2, AS Unit 2: Waves by Mr A on 22 Jan 2010

## Investigating Resistance Wire

Posted in AQA GCSE P2, P2: Current Electricity by Mr A on 20 Jan 2010

## Waves Questions 1

Posted in AQA AS Unit 2, AS Unit 2: Waves by Mr A on 9 Jan 2010

## Electrical Power

Posted in AQA GCSE P1a, P1a: Electrical Devices by Mr A on 9 Jan 2010

This slideshow starts with energy changes, particularly in electrical devices. Various devices are presented as discussion points.

The concept of Power is introduced, along with the equation P=E/t

Electrical Power Slideshow

## Introduction to Waves

Posted in AQA AS Unit 2, AS Unit 2: Waves by Mr A on 7 Jan 2010

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Transverse and longitudinal waves, sometimes called s-waves and p-waves respectively, are demonstrated in these videos. Transverse waves oscillate perpendicular to the direction of motion, and longitudinal waves oscillate in the direction of motion.

Frequency, Wavelength and Wave Speed

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Extras