Light waves which are superposed on each other can only
interfere if they are also coherent. The requirement which must be
fulfilled in order to bring about coherence can be represented as
Hence, coherence is dependent on the spatial dimension (i.e. the
experiment width d of the Iight aperture) and on the
utilized angle of reflection (of the triple slit). Since the
dimensions of the diffraction object (triple slit) are small by
comparison with the distance a of the light source from the
diffraction object, it is true that
=(D/2)/a. This means that students can
make a note of the coherence requirement in the form given above.
To verify this formula, d, D and a must
be measured. The object of the first experiment is to verify the
coherence requirement for red light.
In the second experiment the students should find proof that,
when the magnitude of the Iight source remains constant, long-wave
Iight is more likely to fulfill the coherence requirement than
- Multifunctional light box - All-in-one: Can be used for geometric optics on the table, colour mixing and on an optical bench
- Extension with others sets at anytime, no additional light sources needed, recognition value for students
- When red Iight is diffracted from a triple slit, investigate
the critical width d of the Iight aperture at which
secondary interference maxima just occur or disappear.
- After that, find out whether green or blue light is brought to
interference at the established aperture width d.