Introduction to Photoelasticity

Quick questions

You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

1. Which of the following is the best definition of isotropic?

   	a	Invariant with respect to time
   	b	Invariant
   	c	Invariant with respect to all material properties
   	d	Invariant with respect to direction

2. How many permitted vibration directions does plane polarised light have?

   	a	None
   	b	Two
   	c	One
   	d	Infinite number

3. What does Δn represent in the equation for the Stress-Optic Law?

   	a	Thickness of material
   	b	Stress-Optical coeffcient
   	c	Birefringence
   	d	Stress

4. What are the quantities on the axes of a Michel-Levy chart?

   	a	Retardation against thickness of specimen
   	b	Birefringence against thickness of specimen
   	c	Birefringence against time
   	d	Retardation against time

5. What is the difference between isochromatic and isoclinic fringes?

   	a	Isochromatic fringes are obtained using monochromatic light, whereas isoclinic fringes are obtained using white light.
   	b	Isoclinic fringes are obtained when the principal stress direction coincides with the polarisation of the polariser; isochromatic fringes are lines of constant stress difference.
   	c	Isochromatic and isoclinic fringes occur in different types of plastic.
   	d	Isoclinic fringes are lines of constant stress difference; isochromatic fringes are obtained when the principal stress direction coincides with the polarisation of the polariser.