REFRACTIVE ERRORS 1 - Light - Al-Mustaqbal University

‫جامعة المستقبل‬ ‫كلية التقنيات الصحية والطبية‬ ‫قسم تقنيات البصريات‬ Second Stage 2024-2025 REFRACTIVE ERRORS 1 Lecture Title Light Lecture Number: 1 / course 1 Prepared by Hassan A. Aljaberi OPTOMETRIST 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬...

‫جامعة المستقبل‬ ‫كلية التقنيات الصحية والطبية‬ ‫قسم تقنيات البصريات‬ Second Stage 2024-2025 REFRACTIVE ERRORS 1 Lecture Title Light Lecture Number: 1 / course 1 Prepared by Hassan A. Aljaberi OPTOMETRIST 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬ ‫ حسن عبد الهادي الجابري‬/ ‫مدرس المادة‬ Light Light is a form of electromagnetic radiation that is visible to the human eye. It is one of the fundamental ways energy is transferred through space. Electromagnetic Radiation ‫اإلشعاع الكهرومغناطيسي‬ - Light is part of the electromagnetic spectrum, which includes other forms of radiation such as radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. ‫ المرحلة الثانية‬/ ‫قسم تقنيات البصريات‬ 1 ‫ كلية التقنيات الصحية والطبية‬/ ‫جامعة المستقبل‬ 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬ ‫ حسن عبد الهادي الجابري‬/ ‫مدرس المادة‬ Speed of Light ‫رسعة الضوء‬ - In a vacuum, light travels at a constant speed of approximately 3×108 m/s. - The speed of light changes when it passes through different media (like water or glass), slowing down as it enters denser materials. Interaction with Matter ‫التفاعل مع المادة‬ - When light interacts with matter, it can be absorbed, reflected, refracted, or transmitted depending on the material’s properties and the light’s wavelength. - The color we perceive in objects is due to the wavelengths of light that are reflected from the object to our eyes, with other wavelengths being absorbed. Visible Spectrum ‫الطيف المرئي‬ - The part of the electromagnetic spectrum that is visible to the human eye is known as the visible spectrum, ranging from approximately 400 nanometers (violet) to 700 nanometers (red). - Different wavelengths within this range correspond to different colors, from violet to red. ‫ المرحلة الثانية‬/ ‫قسم تقنيات البصريات‬ 2 ‫ كلية التقنيات الصحية والطبية‬/ ‫جامعة المستقبل‬ 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬ ‫ حسن عبد الهادي الجابري‬/ ‫مدرس المادة‬ Importance of Light ‫أهمية الضو يء‬ - Light is essential for vision, allowing us to see the world around us. - It plays a crucial role in processes like photosynthesis, which is vital for life on Earth. - Light is also used in various technologies, including communication, medicine, and energy. Behaviour of Light ‫سلوكيالضو يء‬ Light rays can travel in different directions or the same direction. Types of light rays include: parallel light rays: Light travels from an object into our eyes by moving in straight lines. These lines are called light rays. Figure 1: Parallel light rays convergent light rays: Convergent light rays will meet at a focal point. Figure 2: Convergent light rays converge to a focal point ‫ المرحلة الثانية‬/ ‫قسم تقنيات البصريات‬ 3 ‫ كلية التقنيات الصحية والطبية‬/ ‫جامعة المستقبل‬ 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬ ‫ حسن عبد الهادي الجابري‬/ ‫مدرس المادة‬ divergent light rays: Divergent light rays come from an object less than 6 m from the eye. Figure 3: Divergent light rays Optical Medium ‫ي‬ ‫الوسطيالبرص ي‬ Light rays can travel through any transparent (clear) material. A transparent material that lets light travel through it is called an optical medium. An optical medium can be a: gas (like air) liquid (like water) solid (like glass or clear plastic) Refractive Index ‫معاملياالنكسا ير‬ Every optical medium has a specific refractive index. It is the ratio of the speed of light in a vacuum to that in a second medium of greater density Light travels faster in a medium that has a low refractive index (like air), and slower in a medium that has a high refractive index (like glass). 𝒔𝒑𝒆𝒆𝒅 𝒐𝒇 𝒍𝒊𝒈𝒉𝒕 𝒊𝒏 𝒂𝒊𝒓 𝒓𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒗𝒆 𝒊𝒏𝒅𝒆𝒙 = 𝒔𝒑𝒆𝒆𝒅 𝒐𝒇 𝒍𝒊𝒈𝒉𝒕 𝒊𝒏 𝒎𝒆𝒅𝒊𝒖𝒎 Examples of refractive index are: Air = 1 Water = 1.333 Crown glass = 1.52 Flint glass = 1.62 Diamond = 2.42 Aqueous humour = 1.336 Cornea = 1.376 Crystalline lens = 1.386 – 1.406 ‫ المرحلة الثانية‬/ ‫قسم تقنيات البصريات‬ 4 ‫ كلية التقنيات الصحية والطبية‬/ ‫جامعة المستقبل‬ 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬ ‫ حسن عبد الهادي الجابري‬/ ‫مدرس المادة‬ Reflection ‫س‬ ‫النعكا ي‬ ‫اي‬ light ray will bounce off a surface when it reaches a smooth reflecting surface, such as a mirror. Law of reflection: angle of incidence = angle of reflection Figure 4: Reflection Refraction ‫االنكسار‬ When a light ray travels from a medium with a lower refractive index into a medium with a higher refractive index, the‫ي‬light ray is bent towards the normal. Figure 5: Refraction 𝒏𝟏 𝐬𝐢𝐧 𝜽𝟏 = 𝒏𝟐 𝐬𝐢𝐧 𝜽𝟐 snell’s law When a light ray travels from a medium with a higher refractive index (high density) into a medium with a lower refractive index (low density), the light ray is bent away from the normal. “VICE VERSA” ‫ المرحلة الثانية‬/ ‫قسم تقنيات البصريات‬ 5 ‫ كلية التقنيات الصحية والطبية‬/ ‫جامعة المستقبل‬ 1 ‫ فصل‬1 )‫أخطاء إنكسار (نظري‬ ‫ حسن عبد الهادي الجابري‬/ ‫مدرس المادة‬ 1. Definitions and Concepts (Short Answer) a) Define the term electromagnetic radiation and explain where light fits within the electromagnetic spectrum. b) What is the speed of light in a vacuum, and how does it change when light passes through a medium such as glass or water? c) Explain the difference between parallel, convergent, and divergent light rays. Provide examples of where each type might be encountered in daily life. d) What is the refractive index? List the refractive index for air, water, and the cornea. 2. Problem-Solving (Calculations) a) A light ray travels from air into water. If the angle of incidence in the air is 30°, calculate the angle of refraction in the water. b) b. Consider a light ray traveling from crown glass to air. If the angle of incidence in the glass is 45°, calculate the angle of refraction in the air. 3. Reflection and Refraction (Essay) Write a short essay (300-500 words) on how reflection and refraction of light are used in designing optical instruments, such as eyeglasses, cameras, or microscopes. Discuss the importance of understanding these concepts in the field of optometry. ‫ المرحلة الثانية‬/ ‫قسم تقنيات البصريات‬ 6 ‫ كلية التقنيات الصحية والطبية‬/ ‫جامعة المستقبل‬