Questions
Calculate the power of a lens having a focal length of 25 cm.
When a ray of light falls on the surface of a plastic block, the angle made by the ray with the normal and the angle of refraction is found to be 45o and 33o respectively. Calculate the refractive index of the plastic.
The refractive index of a diamond is 2.42. If the speed of light in air is $\rm 3 \times 10^{8}$ m/s, calculate the speed of light in a diamond.
If the speed of light in air and glass are $\rm 3 \times 10^{8}$ m/s and $\rm 2 \times 10^{8}$ m/s respectively, then calculate the refractive index of glass with respect to air.
What is a cataract? Write the role of the intraocular lens developed by Nepal's opthalmologist Dr. Sanduk Ruit in the treatment of cataracts.
Explain the laser surgery method used to solve eyesight problems.
Compare the use of spectacles and the use of contact lenses to correct visual defects.
A student concludes that ‘The effect of defect of vision is more on a person wearing spectacles with thick lenses than one wearing that with thin lenses.’ Is this understanding correct? Justify with appropriate reasons.
Explain, with a ray diagram, the role of the lens used to correct long-sightedness.
A student is the class has difficulties in seeing the letters written on the whiteboard when he sits on the last bench but he sees them clearly when he sits on the first bench. Based on this, answer the following questions:
- What type of defect of vision does the student have?
- Draw a ray diagram showing this type of defect of vision of the student.
- Write any two reasons for this defect.
- Explain, with a ray diagram, the role of the lens used to correct this defect.