Why Do You Use A Red Filter In Colorimeter

Red green and blue.

Why do you use a red filter in colorimeter. With the red filter for example clouds contain a lot of red light because theyre pure white when theyre lit by the sun. It works by shining an internal light source onto the surface of the sample. Using an internal light source a colorimeter shines light down onto the surface of the sample.

As you turn the wavelength control knob you will see the light reflected by the paper change from violetblue about 400 nm to green to yellow to orange and finally to red about 700 nm. In the Benedicts test Benedicts solution is blue and the positive result is red - therefore if measuring absorption on a scale where more absorption equates to a higher concentration of reducing sugar a red filter will need to be used. Similarly a book cover appears red since it absorbs all colours except red.

The size of the filter initially chosen for the colorimeter is extremely important as the wavelength of light that is transmitted by the colorimeter has to be same as that absorbed by the substance. A colorimeter also known as a filter photometer is an analytical machine that acts as the tool quantify a solutions concentration by measuring the absorbance of a specific wavelength of light. A colorimeter consists of changeable optics filters which select the wavelength that the solution absorbs the most in order to maximize accuracy.

If a solution is clear and colourless it has not absorbed any visible radiation and therefore all the white light is. The way coloured filters work is that they let in more of a certain type of coloured light the colour of the filter and block the opposing colours. In this experiment red light from the LED light source will pass through the solution and strike a.

The lamp inside the instrument produces white light a mixture of all wavelengths but the wavelength control knob screens all but the one you select. Waves with higher frequency than extreme violet are called ultraviolet and those with lower frequency than extreme red are called infrared. The colorimeter should be set to the red filter.

As the light reflects back up to the device it passes through three filters. Place known samples into cuvette and measure the absorbance of each using the colorimeter. Report 3 years ago.