Hooke's law essentially defines:

CONCEPT:

​Hooke's law

• Hooke's law states that within the elastic limit the stress applied on a body is directly proportional to strain produced.

⇒ Stress ∝ Strain

⇒  Stress = E × Strain

Where E = modulus of elasticity

⇒  σ = Eϵ    

where σ = stress, ϵ = strain, and E = young's modulus of elasticity

EXPLANATION:

• Hooke's law states that within the elastic limit the stress applied on a body is directly proportional to strain produced.
• So the Hooke's law defines the elastic limit. Hence, option 3 is correct.