Understanding Refraction

Refraction
This pencil appears to bend when it enters
the water because of the change in the light
ray speed as the medium changes.
Refraction is the directional change of wave propagation caused by a change in the light beams transmission medium.

Light rays travel through space in a straight line at approximately 300,000 km/s. As light passes through a transparent medium, such as water or glass, its speed is decreased.

For glass, its reduced to 200,000 kilometers per second, and for water the speed is 225,000 kilometers per second.

If the light enters into a medium perpendicular to the surface, it passes straight through but at a slower speed. However if the light beam arrives at the medium surface at an angle, not only will it speed be reduced, but it will bend due to a process called refraction.

As a beam of light reaches the surface of a medium the lower portion enters first and is slow down. However, the upper portion is still traveling at the speed of light until it arrives at the surface and enters. This speed difference at the top and bottom aspects of the light path causes it to pivot, bending toward what is referred to as the normal. This is an imaginary line drawn perpendicularly to the surface of the material.
 
Transparent materials have what is called a refractive index. This is the speed at which light travels in a medium compared to like traveling in a vacuum.
   
For example, typical glass has a refractive index of 1.33. This is calculated by dividing the speed of light in a vacuum (300,000 km/s) by the speed of light in glass (225,000 km/s).
   
The refractive index of air is 1.0003. Anytime a light beam travels from a medium with a low index of refraction, like air, to a medium with a higher index of refraction, like glass, the beam of light will bend toward the normal.
   
Likewise when the beam of light exits a highly refractive medium into a medium with the low index of refraction, the process is reversed.
   
The bottom portion of the beam of light exits first, and resumes at the speed of light, with the top portion still at the speed determined by the medium. This causes the beam to pivot away from the normal line.

Instruments used to measure the refractive index are called refractometers. Refractometers used in industrial automated systems are referred to as inline refractometers.

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The Preparation of Pharmaceutical Waters

Pharmaceutical Waters
While the public considers municipal water to be “pure”, the pharmaceutical market considers municipal water (feedwater) just the starting point in producing pure water. Water is the most widely used excipient in pharmaceutical manufacturing, and pharmaceutical water is a multi-functional resource, crossing all disciplines in the pharmaceutical industry. Water is used as a raw material, solvent, ingredient, reagent, and clean-ing agent, and is produced in a variety of “pure” forms.

Purified Water (PW), Highly Purified Water (HPW), and Water for Injection (WFI) used in pharmaceutical processes are produced on site from the local potable water, which has been produced by the treatment of the feedwater.

This best practice guide, titled "Pharmaceutical Waters Guide for Regulatory Compliance, Analysis and Real-Time Release" and produced by Mettler Toledo Thornton, provides insight on the following topics:

DOWNLOAD THE FULL GUIDE HERE.

Pharma Waters Overview


  • The Preparation of Pharmaceutical Waters
  • Pharmacopeia Overview
  • Industry Trends for Pharmaceutical Waters

Process Analytical Technology (PAT) and Intelligent Sensor Management (ISM)


  • Ensuring Pharmaceutical Water Compliance in a PAT Environment

Total Organic Carbon


  • Total Organic Carbon Measurement is a Key Control Point for Pharmaceutical Water Systems
  • Improving Water System Performance Continuous Real-Time TOC Measurements
  • Case Study: Real-Time TOC Analysis Safeguards Water Purity
  • Case Study: In-line TOC Monitoring: Reduces Production Downtime
  • Case Study: Leading Water Treatment Solution Provider Chooses METTLER TOLEDO Thornton
  • The Value of Measuring TOC in CIP and Cleaning Validation Applications

Conductivity/Resistivity


  • Ensuring the Absence of Ionic Impurities with Conductivity/Resistivity Measurements
  • Calibration Solutions for Pharmaceutical Waters
  • Case Study: Clean in Place Systems Manufacturer Relies on METTLER TOLEDO

Ozone


  • Reliable, Cost-effective Sanitization the Power of Ozone
  • Application and Control of Ozone Sanitization for Pharmaceutical Waters
  • Case Study: Critical Ozone Measurement in Purified Water Systems