Difference Between Diffraction and Refraction

Diffraction vs Refraction

Diffraction and refraction are both wave properties. They sound similar, as both represent some sort of bending of waves. For instance, if we put a straw in to a glass of water, it appears to be broken. That happens due to the refraction of light waves. Using a ripple tank we can observe how the water waves bend when it encounters an obstacle.


Waves bend around small obstacles and spreads out at small openings in entering into a region that would otherwise be shadowed. Such deviation of the wave from its initial straight-line path is called diffraction. Diffraction of waves results in a dark and bright fringe pattern identified as “diffraction pattern”. Also, when light waves travel through media with different refractive indices or when sound waves travel through the medium of different acoustic impedances, diffraction effects can be observed. Generally, diffraction effects are most pronounced when the dimensions of the obstacle nearly agrees with the wavelength of the wave. When light waves are diffracted by a single slit, the result is a diffraction pattern with bright and dark fringes. The central bright fringe has the maximum intensity and width. Intensity of the fringes decreases as we move along either side of the central maxima.


When a wave passes from one medium to another at any angle except 90° and 0°, its line of travel changes at the interface due to the change in velocity of the wave. This is what we call refraction. Although light waves provide most of the examples for refraction, any other wave can also refract. For instance, sound waves refract when they cross two media, water waves refract depending on the depth. Refraction is always accompanied by a wavelength and speed change, which is decided by the refractive indices of the media. Refraction of light waves is the most common observation, since they produce strange optical illusions. The formation of beautiful rainbows, splitting of white light by a glass prism, and mirages are some examples.

What is the difference between Diffraction and Refraction?

Both diffraction and refraction involve change of direction of waves. When a wave encounters an obstacle, bending or spreading occurs, which we call diffraction. On the other hand, waves refract when they travel from one medium to another. Light waves, when diffracted result in a diffraction pattern, whereas when they are refracted some sort of visual distortion may take place. Diffraction and refraction both can split the white light in to separate colors. When white light is sent through a glass prism it refracts and splits according to the wavelengths of each color, because the refractive index of glass is different from that of air. Similarly, we can observe the rainbow pattern on a CD or DVD, since they act as diffraction gratings.

Difference Between Diffraction and Refraction

• Diffraction is bending or spreading of waves around an obstacle, while refraction is bending of waves due to change of speed.

• Both diffraction and refraction are wavelength dependant. Hence, both can split white light in to its component wavelengths.

• Diffraction of light produces a fringe pattern, whereas refraction creates visual illusions but not fringe patterns.

• Refraction can make objects appear closer than they really are, but diffraction can not do that.