# Hard Cocoa Posts

## IGCSE Definitions

Radioactive decay is both random over space and time, and radioactive decay is spontaneous.

### Random

Random over space means that given a large number of radioactive nuclei, it would be impossible to predict which nuclei would decay next. Random over time means that you cannot predict when a nuclei would decay at any time.

Given a large number of nuclei, it can be safe to predict that approximately half of the original radioactive nuclei would decay after one half-life. However, the exact number of nuclei decay would not be identical given two samples of equal number of original radioactive nuclei.

## Ultrasound Calculations

The table provides the data for the acoustic impedance and absorption coefficients for muscle and bone. A parallel beam of ultrasound of intensity  enters the muscle of thickness 3.0 cm…

## Cambridge A-Level Definitions

This post contains the definitions used in the A-level curriculum. A-level Definitions Motion in a circle Radian One radian is defined as the angle subtended at the centre of a…

## Types of Ultrasound Scans

We will investigate two types of ultrasound scans. A-Scan This is a simple type of scan. A pulse of ultrasound is sent into the tissue and the echoes are detected…

## Ultrasonic Production and Detection

Production Sound is created when a surface vibrates, pushing the medium particles into a series of compressions and rarefactions. A human being would normally be able to hear sound with…

## Lesson 9 – Vectors

In the previous lesson, we learnt about arrays. Arrays are containers that store data. In order to declare an array, you need to specify what type of data it stores,…