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Written by Palak Mall, Senior Content Writer · reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory supply · updated 17 October 2026

Gratings & Filters lists 10 items for diffraction, interference and colour work in school and college optics labs: five transmission diffraction gratings, a slide carrying three gratings, three photographic diffraction diaphragms with slits, discs and holes, and a set of seven colour filters. Sizes and line counts below are the ones given in each listing.

Diffraction gratings

Grating	Line count in the listing	What the listing specifies
Diffraction Grating 100 Lines	100	Transmission grating mounted on a glass carrier, 38 x 50 mm
Diffraction Grating 300 Lines	300	Transmission grating mounted on a glass carrier, 38 x 50 mm
Diffraction Grating 1000 Lines	1000	Transmission grating mounted on a glass carrier, 38 x 50 mm
Diffraction Grating 7500 Lines	7500	Transmission grating mounted on a glass carrier, 38 x 50 mm
Diffraction Grating 15000 Lines	15000	Transmission grating mounted on a glass carrier, 38 x 50 mm
Diffraction Grating Slide	100, 300 and 600 lines/mm	Three diffraction gratings on one frame

The five single gratings share one format, a 38 x 50 mm glass carrier, and are listed for spectroscopic examinations and for experiments on diffraction and interference. They differ only in the line count given in each name, so quote that figure when ordering. The Diffraction Grating Slide is the one to use for showing how line spacing controls the diffraction angle: with 100, 300 and 600 lines/mm side by side, the finer gratings spread the orders further apart.

Diffraction diaphragms

Three photographic diffraction objects are mounted in 50 x 50 mm slide frames.

Diaphragm	What the listing specifies
Diaphragm with 3 Single Slits and 1 Double Slit	Single slits 0.075, 0.15 and 0.4 mm wide; one double slit with 0.1 mm slits at 0.5 mm spacing
Diaphragm with 9 Different Discs	Nine opaque discs from 0.1 to 1.8 mm in diameter
Diaphragm with 9 Different Holes	Nine holes from 0.1 to 1.8 mm in diameter

The slit diaphragm carries three single slits, so a class can watch the central maximum widen as the slit narrows from 0.4 to 0.075 mm, and then move to the double slit for interference fringes. The disc and hole diaphragms cover the same diameter range. A disc and a hole of equal size are complementary objects, and by Babinet’s principle they give the same diffraction pattern away from the central spot.

Colour filters

The Colour Filters, Primary & Secondary set holds seven plastic transparencies, each fitted between glass plates in a slide frame: red, green and blue, with cyan, magenta, yellow and violet. It is listed for both additive and subtractive colour mixing.

Additive mixing: beams of red, green and blue light overlapping on a white screen. Red and green give yellow, and all three together give white.
Subtractive mixing: filters stacked in one beam. Each filter removes part of the spectrum, so cyan and yellow together pass only green.

Holding the gratings on a bench

For optical bench work, the Optical Bench Gratings Holder in Optical Bench & Accessories is a square metal sheet with a centred circular aperture and two clips to hold gratings of different sizes. A grating can also be held on the prism table of a spectrometer to measure wavelengths.

Related ranges

This range is part of Light & Optics. Spectrometers and gas spectrum tubes are under Spectrometers and Spectrum Tubes, the bench, slits and screens under Optical Bench & Accessories, and ray boxes and spectral lamps under Apparatus & Kits.

Questions buyers ask

How do the five diffraction gratings differ?
Only in the line count in each name: 100, 300, 1000, 7500 or 15000. All are transmission gratings on a 38 x 50 mm glass carrier.

What slit widths are on the slit diaphragm?
The Diaphragm with 3 Single Slits and 1 Double Slit has single slits of 0.075, 0.15 and 0.4 mm and a double slit of 0.1 mm slits spaced 0.5 mm apart, in a 50 x 50 mm slide frame.

Which colours are in the filter set?
Seven: red, green, blue, cyan, magenta, yellow and violet.

Is there a grating with several line spacings on one mount?
Yes. The Diffraction Grating Slide carries three gratings of 100, 300 and 600 lines/mm on one frame.