Demonstrations. - Expose a photographic dry plate to daylight. Develop it and fix it. Wash it thoroughly and dry it. With a fine needle or the point of a knife blade draw a series of parallel lines through the film to the glass. Hold this plate close to the eye and look through it at the flame of a candle. There will be seen brilliant spectrum colors extending on either side of the flame.

On one half of the plate used above, draw two sets of parallel lines at right angles to each other, dividing the film into small squares. Look through this at an arc or incandescent light, and fine lines of spectra will be seen to extend at right angles from the light.

A fine silk handkerchief gives a good effect when looked through, especially when the light examined is an arc light. A plate of glass upon which a little lycopodium powder has been sprinkled gives a series of beautiful rainbow effects when a candle or any bright light is seen through it. The cause of these phenomena is that rays of light on passing through a narrow slit spread out into a diverging band, or are diffracted; and if the edges of the slit are near each other, interference takes place and gives colored fringes.

The diffraction grating consists of from 10,000 to 20,000 parallel lines to the inch, ruled on glass or on speculum metal. If on the former, the light passes through, if on the latter, it is reflected from the polished and ruled surface. Spectra of wide dispersion can be obtained from such gratings, and they are used in place of the prism in spectroscopic work. The spectrum given by the grating is called the normal spectrum, since in it the distribution of the different wave lengths is uniform.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم الشؤون الطبية يقدم الخدمات الصحية والعلاجية لزائري مدينة سامراء

العتبة العباسية المقدسة تقدم خدماتها لزائري مرقد الإمامين العسكريين (عليهما السلام) في سامراء

المجمَع العلمي ووفد وزارة التربية يبحثان سبل التعاون المشترك

قسم الشؤون الفكرية يصدر العدد 192 من مجلة الرياحين للأطفال

المزيد

الآخبار الصحية

كنز غذائي على طبقك.. ماذا تفعل السبانخ بجسمك؟

ما لا يتوقعه أحد.. "سر غذائي" في الجبن الدسم

لتحسين الهضم والنوم.. هذا أفضل وقت لتناول العشاء

10 طرق بسيطة وغير مألوفة لحرق المزيد من السعرات يوميا

المزيد

الآخبار التكنلوجية

سابقة بعالم الطيران.. طائرة تقرر الهبوط بنفسها بعد ظرف طارئ

"الإنفلونزا الخارقة" تكتسح دول العالم.. وتثير قلقا كبيرا

مرحلة ما قبل الأعراض.. دواء جديد يستهدف "شرارة" الزهايمر

إزالة ثاني أكسيد الكربون من الغلاف الجوي.. ما دور المحيطات والبحار؟

المزيد

مواضيع ذات صلة

Angles of Incidence and Refraction

The Laws of Refraction

Polarized Light

Indices of Refraction

The Propagation of Light

Spherical Aberration

Double Refraction

الضوء

The Color of Transparent Bodies

The Color of Opaque Bodies

The Secondary Bow

Why the Rainbow is Circular